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Time-Lag in Identification of Fertility in Broad Breasted Bronze Eggs and Its Relation to Hatchability and, Possibly, Parthenogenesis1,2
Time-Lag in Identification of Fertility in Broad Breasted Bronze Eggs and Its Relation to Hatchability and, Possibly, Parthenogenesis1,2 I. L.
KOSIN
Department of Poultry Science, State College of Washington, Pullman (Received for publication March 3, 1958)
ment in turkeys to be related to hatchability: those eggs hatched best in which the condition of fertility could be identified by candling within 24 hours of setting. Furthermore, no eggs hatched which took more than 72 hours to reach a stage at which they could be classified, by candling, as "fertiles." The accuracy of identifying fertility in turkey hatching eggs, by candling, following a period of incubation, can range all the way down to nearly 80% (Kosin et al., 1951, and unpublished data). It has been postulated that some of these underdeveloped or retarded embryos represent cases of early death or of moribund blastoderms, being, in any event, the product of essentially normal fertilization (Kosin, 1951). On the other hand, Olsen and Marsden (1954) have suggested that at least some of these in reality are instances of parthenogenetic development. The resolution of this basically important question is predicated on finding recognizable differences between fertilized and non-fertilized, but developing, germ discs in the eggs of mated hens. The report of Yao and Olsen (1955) that par1
Scientific paper No. 1702. Washington Agricultural Experiment Stations, Pullman. Projects Nos. 803 and 1190. 2 Supported, in part, by Federal Funds for Regional Research (W-7) under the Hatch Amended Act and by funds for Biological and Medical Research provided by State of Washington Initiative No. 171.
thenogenetic turkey embryos are diploid, appears to rule out cytology as a tool in making this differentiation, if the cytological detail is generally as clear cut as their data seem to indicate. In view of this existing impasse in the question of the degree of involvement of parthenogenesis in eggs from mated hens, an indirect approach suggested itself for studying the problem. If one could alter the frequency of such retarded embryos, as well as ameliorate the effect of such retardation on subsequent hatchability, one could reasonably question the pertinence of parthenogenesis. Accordingly, an investigation was undertaken in May, 1955, the results of which are herein reported. MATERIALS AND METHODS
The eggs were collected from 24 singlesire Broad Breasted Bronze breeding pens. These eggs were also utilized in the preincubation warming study (Kosin and St. Pierre, 1956). This fact permitted making observations on the effect of age of egg at time of setting (1-14 days) and of certain warming treatments on the initial rate of embryonic growth and subsequent hatchability. The eggs were set every two weeks. Three hatches in all were included in the present investigation which involved 2,710 fertile eggs. The first candling of the eggs was 36 hours after setting, followed for five days by candlings at 24-hour intervals. Candling was carried out with the aid of Fer-Tell-Egg candler (Bundy). At the end of 65 days of incubation, all "infertile"
1150
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on April 18, 2015
and Marsden (1954) observed O LSEN the rate of early embryonic develop-
1151
TIME-LAG AND FERTILITY IDENTIFICATION T A B L E 1.—Distribution of fertility and hatchability according to time-lag identification of fertility (by candling)
in
Time-lag stages: N o . of h o u r s after which fertility could be identified w a s : 36 60 84 108 132
1S6
Pre-incubation storage age (in days) 1-7
1-7
8-14
94.2 87.5
3.9
9.3
98.7 94.0 67.8 58.8
1.3 20.0
5.6 30.4
8-14
1-7
8-14
0.3
0.5
1-7
8-14 0.03
0.4 0.8
8-14 day eggs fell into the 60-hour classification. Indeed, in a few hatched eggs of this storage group, the condition of fertility could not be identified until 84 hours of incubation. Moreover, the two storage egg groups differed in actual hatchability. The surprising feature here was the marked depression of hatchability in those 1-7 day eggs in which fertility was identifiable at 60 hours, as compared with the corresponding group of the 8-14 day RESULTS eggs. Table 1 shows that fertile eggs of In line with these observations on the shorter storage history (1-7 days) devel- effect of setting age of the egg on its initial oped more rapidly on the whole. After 36 development, there is evidence that such hours of incubation, a higher proportion development was affected by at least one of 1-7 day eggs could be identified as "warming" treatment to which the eggs fertiles than was true of 8-14 day eggs. had been subjected prior to final setting. Correspondingly, in the latter group, more As mentioned earlier, the eggs involved eggs needed a longer time-lag for the in- in this study also were used in another shell identification of embryonic develop- investigation concerned with the effect ment. A few of the "older" eggs took 156 of certain pre-incubation treatments of hours ( 6 | days) to develop to a point eggs on their hatchability (for details, where a positive detection of development see Kosin and St. Pierre, 1956). The most could be made by candling. effective of these treatments in raising Paralleling these observations on fertil- hatchability was No 19, in which the eggs ity, the detail of distribution of hatchabil- were subjected to a 5-hour warming at ity in the two storage age groups also was 99f°F. prior to 1-14 day storage. The dissimilar. In the 1-7 day storage eggs, control eggs (treatment 10) were stored at almost 99% of the eggs which hatched fell 53°F. in the 36-hour time-lag stage; the remainThe treatment 19 eggs, which showed ing 1 percent represented eggs in which an improvement of up to 10% in hatchafertility was identified after 60 hours of bility for the 1955 hatching season (Febincubation. Although they showed a ruary-July), also had fewer retarded similar over-all pattern in the distribution early embryos. This was judged by the of hatchability, relatively more of the frequency with which the condition of eggs were broken out and examined for gross signs of development. The fertile eggs were left in the incubator for the balance of the incubation period. Poults were removed on the 29th day (setting day being counted as day 1). The unhatched eggs remained for an additional day in the incubator; however, this precaution was later found to be unnecessary: no poults ever hatched from these "left over" eggs.
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on April 18, 2015
Distribution of fertile eggs (as % of total fertiles) Distribution of hatched eggs (as % of total hatched eggs) Percent hatchability (of fertiles)
1152
I. L. KOSIN
TABLE 2.—Candling errors {percent) in the identification of fertility Control eggs
Pre-heated eggs
Stored for
Stored for
1-7 days
8-14 days
1-7 days
8-14 days
(n=1687) 2.25
(n=1733) 2.10
(n = 1800) 0.89
(n = 1657) 0.85
DISCUSSION The observation that the hatching capacity of an egg declines directly with the length of time-lag necessary for a positive identification of embryonic development fully agrees with the findings of Olsen and Marsden (1954). It contradicts, however, the more recent report of Payne et al. (1957) who did not observe such a trend in eggs in which the condition of fertility was not identified as long as 72 hours after setting. There is no readily available explanation for this conflict in results. Other available evidence on this matter (for example, McNally and Byerly, 1936; Olsen and Marsden, 1950; Kosin and St. Pierre, 1956 and unpublished data from this laboratory) indicates, however, that hatchability in chickens and turkeys is directly related to rate of early embryonic development. Deductively at least, it is difficult to visualize a contrary situation in view of the sharply delimited "natural" incubation period. However it may be, this problem undoubtedly would have to be resolved by further studies. Susceptibility of the initial rate of turkey embryonic development to such environmental influences as age of the egg and pre-incubation handling was not altogether unexpected. Work in this laboratory (Kosin, 1950, and Kosin and St. Pierre, 1956, and unpublished), has pointed in that direction. Perhaps more
An interesting sidelight to the above observations is the distinct possibility that eggs, subjected to a comparatively short period of pre-incubation storage when incubated must, in order to survive, start active development early. The same degree of urgency does not seem to apply to older eggs. A higher proportion of the initially rapidly developing blastoderms in such eggs died than in the case of eggs subjected to shorter storage. However, those eggs stored 8-14 days in which the initial development was slower had a better chance of survival than the comparable "fresher" eggs. As a working hypothesis, it is suggested that those blastoderms which are extremely susceptible to the effects of storage are eliminated early in incubation. The survivors then would represent genetically superior individuals, from standpoint of hatchability, and therefore, should be desirable genetic material for propagation. This is in line with the evidence obtained by Abplanalp and Kosin (1953) that heritability of hatchability was higher in "older" eggs which would lead to greater effectiveness of natural selection.
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on April 18, 2015
fertility was found, on break-out, in the candled "infertile" eggs following seven days' incubation (Table 2).
significant is its implication in regard to the suggestion of Olsen and Marsden (1954) that parthenogenesis may be a factor in the occurrence of retarded early embryos. Admittedly, the data presented here still do not completely eliminate the possibility of the existence of such involvement, but its probability appears to be less likely. Thus far there is no evidence which indicates that the pattern of development of a parthenogenetic embryo can be altered, particularly in the direction of increased rate of its occurrence, by such means as were employed in this study. This does not eliminate, however, the possibility of the existence of "activators" of parthenogenetic development in turkey eggs (Olsen, 1956; and Kosin, 1955).
TIME-LAG AND FERTILITY IDENTIFICATION SUMMARY
REFERENCES Abplanalp, H., and I. L. Kosin, 1953. Genetic variation of fertility and hatchability in the Broad Breasted Bronze turkey. Poultry Sci. 32:321-331.
Kosin, I. L., 1950. A relationship between the length of storage and incubation periods in Broad Breasted Bronze eggs. Poultry Sci. 29: 620-621. Kosin, I. L., 1951. A study of the morphology of moribund turkey blastoderms. Official Reports, 9th World's Poultry Congress 3: 75-87. Kosin, I. L., 1955. Parthenogenetic development of a turkey egg germ disc following a period of incubation or storage. Supplement to Progress Reports of the Poultry Council of the State College of Washington, November, pp. 74-78. Kosin, I. L., and E. St. Pierre, 1956. Studies on preincubation warming of chicken and turkey eggs. Poultry Sci. 35: 1384-1392. Kosin, I. L., E. St. Pierre and R. McLaughlin, 1951. The prevalence of early embryonic mortality in the Broad Breasted Bronze turkeys. Poultry Sci. 30: 805-814. McNally, E. H., and T. C. Byerly, 1936. Variation in the development of embryos of hens' eggs. Poultry Sci. 15: 280-283. Olsen, M. W., and S. J. Marsden, 1950. Variability among turkey embryos at twenty-four hours of incubation with respect to hatchability. Poultry Sci. 24: 414-419. Olsen, M. W., and S. J. Marsden, 1954. Mortality among turkey embryos in relation to rate of embryonic development. Poultry Sci. 33: 11461151. Olsen, M. W., 1956. Fowl pox vaccine associated with parthenogenesis in chicken and turkey eggs. Science, 124: 1078-1079. Payne, L., L. Ortman and P. B. Siegel, 1957. Early detection of fertility in turkey eggs in relation to "shuck-outs". Poultry Sci. 36: 576-579. Yao, T. S., and M. W. Olsen, 1955. Microscopic observations of parthenogenetic embryonic tissues from virgin turkey eggs. J. Heredity, 46: 133-134.
NEWS AND NOTES (Continued from page 1143) cal Society of America was formed, and this Section is now linked with the Association. An Associate Editor from the United States has been appointed as well as several members of the Editorial Board. In order to preserve continuity, the first volume of Animal Behaviour is numbered Volume VI. It is published twice a year in March and September at an annual subscription of 50 shillings. Manuscripts should be sent to The Editors, Animal Behavior, Nutritional Research Unit, Huntingdon, England, or in the case of contributions from
the United States to D. E. Davis, School of Hygiene and Public Health, Johns Hopkins University, Baltimore 5, Md. The Editor is A. N. Worden, with B. A. Cross (Cambridge) and D. E. Davis (Baltimore) as Associate Editors. The other members of the Editorial Board are L. R. Aronson (New York), J. D. Carthy (London), N. E. CoUias (Carbondale), J. T. Eayrs (Birmingham), A. E. Emerson (Chicago), J. T. Emlen (Madison), G. C. Grindley (Cambridge), E. B. Hale (University Park), John Hammond (Cambridge), L. H. Matthews (London), E. Hess
(Continued on page 1255)
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on April 18, 2015
Broad Breasted Bronze hatching eggs, stored 1-7 and 8-14 days prior to incubation, were first candled 36 hours following setting and then once daily for the next 5 days. 2,710 eggs were involved. The time-lag necessary for the initial in-shell detection of fertility was determined and related to hatchability. A higher proportion of the 1-7 day eggs showed a definite tendency to "start" development 36 hours after setting (as indicated by candling appearance) and to hatch better than did the 8-14 day eggs. Some of the latter showed no identifiable signs of development until the 156th postsetting hour. No eggs which had a timelag longer than 84 hours hatched. The hatchability of those 8-14 day eggs in which fertility could not be identified until 60 hours post setting was higher than that of the 1-7 day eggs. The frequency of retarded embryos was affected by pre-incubation treatment of eggs. Certain inferences are drawn from these observations with respect to the possible prevalence of parthenogenetic development in eggs from mated hens.
1153
KOSIN
Department of Poultry Science, State College of Washington, Pullman (Received for publication March 3, 1958)
ment in turkeys to be related to hatchability: those eggs hatched best in which the condition of fertility could be identified by candling within 24 hours of setting. Furthermore, no eggs hatched which took more than 72 hours to reach a stage at which they could be classified, by candling, as "fertiles." The accuracy of identifying fertility in turkey hatching eggs, by candling, following a period of incubation, can range all the way down to nearly 80% (Kosin et al., 1951, and unpublished data). It has been postulated that some of these underdeveloped or retarded embryos represent cases of early death or of moribund blastoderms, being, in any event, the product of essentially normal fertilization (Kosin, 1951). On the other hand, Olsen and Marsden (1954) have suggested that at least some of these in reality are instances of parthenogenetic development. The resolution of this basically important question is predicated on finding recognizable differences between fertilized and non-fertilized, but developing, germ discs in the eggs of mated hens. The report of Yao and Olsen (1955) that par1
Scientific paper No. 1702. Washington Agricultural Experiment Stations, Pullman. Projects Nos. 803 and 1190. 2 Supported, in part, by Federal Funds for Regional Research (W-7) under the Hatch Amended Act and by funds for Biological and Medical Research provided by State of Washington Initiative No. 171.
thenogenetic turkey embryos are diploid, appears to rule out cytology as a tool in making this differentiation, if the cytological detail is generally as clear cut as their data seem to indicate. In view of this existing impasse in the question of the degree of involvement of parthenogenesis in eggs from mated hens, an indirect approach suggested itself for studying the problem. If one could alter the frequency of such retarded embryos, as well as ameliorate the effect of such retardation on subsequent hatchability, one could reasonably question the pertinence of parthenogenesis. Accordingly, an investigation was undertaken in May, 1955, the results of which are herein reported. MATERIALS AND METHODS
The eggs were collected from 24 singlesire Broad Breasted Bronze breeding pens. These eggs were also utilized in the preincubation warming study (Kosin and St. Pierre, 1956). This fact permitted making observations on the effect of age of egg at time of setting (1-14 days) and of certain warming treatments on the initial rate of embryonic growth and subsequent hatchability. The eggs were set every two weeks. Three hatches in all were included in the present investigation which involved 2,710 fertile eggs. The first candling of the eggs was 36 hours after setting, followed for five days by candlings at 24-hour intervals. Candling was carried out with the aid of Fer-Tell-Egg candler (Bundy). At the end of 65 days of incubation, all "infertile"
1150
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on April 18, 2015
and Marsden (1954) observed O LSEN the rate of early embryonic develop-
1151
TIME-LAG AND FERTILITY IDENTIFICATION T A B L E 1.—Distribution of fertility and hatchability according to time-lag identification of fertility (by candling)
in
Time-lag stages: N o . of h o u r s after which fertility could be identified w a s : 36 60 84 108 132
1S6
Pre-incubation storage age (in days) 1-7
1-7
8-14
94.2 87.5
3.9
9.3
98.7 94.0 67.8 58.8
1.3 20.0
5.6 30.4
8-14
1-7
8-14
0.3
0.5
1-7
8-14 0.03
0.4 0.8
8-14 day eggs fell into the 60-hour classification. Indeed, in a few hatched eggs of this storage group, the condition of fertility could not be identified until 84 hours of incubation. Moreover, the two storage egg groups differed in actual hatchability. The surprising feature here was the marked depression of hatchability in those 1-7 day eggs in which fertility was identifiable at 60 hours, as compared with the corresponding group of the 8-14 day RESULTS eggs. Table 1 shows that fertile eggs of In line with these observations on the shorter storage history (1-7 days) devel- effect of setting age of the egg on its initial oped more rapidly on the whole. After 36 development, there is evidence that such hours of incubation, a higher proportion development was affected by at least one of 1-7 day eggs could be identified as "warming" treatment to which the eggs fertiles than was true of 8-14 day eggs. had been subjected prior to final setting. Correspondingly, in the latter group, more As mentioned earlier, the eggs involved eggs needed a longer time-lag for the in- in this study also were used in another shell identification of embryonic develop- investigation concerned with the effect ment. A few of the "older" eggs took 156 of certain pre-incubation treatments of hours ( 6 | days) to develop to a point eggs on their hatchability (for details, where a positive detection of development see Kosin and St. Pierre, 1956). The most could be made by candling. effective of these treatments in raising Paralleling these observations on fertil- hatchability was No 19, in which the eggs ity, the detail of distribution of hatchabil- were subjected to a 5-hour warming at ity in the two storage age groups also was 99f°F. prior to 1-14 day storage. The dissimilar. In the 1-7 day storage eggs, control eggs (treatment 10) were stored at almost 99% of the eggs which hatched fell 53°F. in the 36-hour time-lag stage; the remainThe treatment 19 eggs, which showed ing 1 percent represented eggs in which an improvement of up to 10% in hatchafertility was identified after 60 hours of bility for the 1955 hatching season (Febincubation. Although they showed a ruary-July), also had fewer retarded similar over-all pattern in the distribution early embryos. This was judged by the of hatchability, relatively more of the frequency with which the condition of eggs were broken out and examined for gross signs of development. The fertile eggs were left in the incubator for the balance of the incubation period. Poults were removed on the 29th day (setting day being counted as day 1). The unhatched eggs remained for an additional day in the incubator; however, this precaution was later found to be unnecessary: no poults ever hatched from these "left over" eggs.
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on April 18, 2015
Distribution of fertile eggs (as % of total fertiles) Distribution of hatched eggs (as % of total hatched eggs) Percent hatchability (of fertiles)
1152
I. L. KOSIN
TABLE 2.—Candling errors {percent) in the identification of fertility Control eggs
Pre-heated eggs
Stored for
Stored for
1-7 days
8-14 days
1-7 days
8-14 days
(n=1687) 2.25
(n=1733) 2.10
(n = 1800) 0.89
(n = 1657) 0.85
DISCUSSION The observation that the hatching capacity of an egg declines directly with the length of time-lag necessary for a positive identification of embryonic development fully agrees with the findings of Olsen and Marsden (1954). It contradicts, however, the more recent report of Payne et al. (1957) who did not observe such a trend in eggs in which the condition of fertility was not identified as long as 72 hours after setting. There is no readily available explanation for this conflict in results. Other available evidence on this matter (for example, McNally and Byerly, 1936; Olsen and Marsden, 1950; Kosin and St. Pierre, 1956 and unpublished data from this laboratory) indicates, however, that hatchability in chickens and turkeys is directly related to rate of early embryonic development. Deductively at least, it is difficult to visualize a contrary situation in view of the sharply delimited "natural" incubation period. However it may be, this problem undoubtedly would have to be resolved by further studies. Susceptibility of the initial rate of turkey embryonic development to such environmental influences as age of the egg and pre-incubation handling was not altogether unexpected. Work in this laboratory (Kosin, 1950, and Kosin and St. Pierre, 1956, and unpublished), has pointed in that direction. Perhaps more
An interesting sidelight to the above observations is the distinct possibility that eggs, subjected to a comparatively short period of pre-incubation storage when incubated must, in order to survive, start active development early. The same degree of urgency does not seem to apply to older eggs. A higher proportion of the initially rapidly developing blastoderms in such eggs died than in the case of eggs subjected to shorter storage. However, those eggs stored 8-14 days in which the initial development was slower had a better chance of survival than the comparable "fresher" eggs. As a working hypothesis, it is suggested that those blastoderms which are extremely susceptible to the effects of storage are eliminated early in incubation. The survivors then would represent genetically superior individuals, from standpoint of hatchability, and therefore, should be desirable genetic material for propagation. This is in line with the evidence obtained by Abplanalp and Kosin (1953) that heritability of hatchability was higher in "older" eggs which would lead to greater effectiveness of natural selection.
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on April 18, 2015
fertility was found, on break-out, in the candled "infertile" eggs following seven days' incubation (Table 2).
significant is its implication in regard to the suggestion of Olsen and Marsden (1954) that parthenogenesis may be a factor in the occurrence of retarded early embryos. Admittedly, the data presented here still do not completely eliminate the possibility of the existence of such involvement, but its probability appears to be less likely. Thus far there is no evidence which indicates that the pattern of development of a parthenogenetic embryo can be altered, particularly in the direction of increased rate of its occurrence, by such means as were employed in this study. This does not eliminate, however, the possibility of the existence of "activators" of parthenogenetic development in turkey eggs (Olsen, 1956; and Kosin, 1955).
TIME-LAG AND FERTILITY IDENTIFICATION SUMMARY
REFERENCES Abplanalp, H., and I. L. Kosin, 1953. Genetic variation of fertility and hatchability in the Broad Breasted Bronze turkey. Poultry Sci. 32:321-331.
Kosin, I. L., 1950. A relationship between the length of storage and incubation periods in Broad Breasted Bronze eggs. Poultry Sci. 29: 620-621. Kosin, I. L., 1951. A study of the morphology of moribund turkey blastoderms. Official Reports, 9th World's Poultry Congress 3: 75-87. Kosin, I. L., 1955. Parthenogenetic development of a turkey egg germ disc following a period of incubation or storage. Supplement to Progress Reports of the Poultry Council of the State College of Washington, November, pp. 74-78. Kosin, I. L., and E. St. Pierre, 1956. Studies on preincubation warming of chicken and turkey eggs. Poultry Sci. 35: 1384-1392. Kosin, I. L., E. St. Pierre and R. McLaughlin, 1951. The prevalence of early embryonic mortality in the Broad Breasted Bronze turkeys. Poultry Sci. 30: 805-814. McNally, E. H., and T. C. Byerly, 1936. Variation in the development of embryos of hens' eggs. Poultry Sci. 15: 280-283. Olsen, M. W., and S. J. Marsden, 1950. Variability among turkey embryos at twenty-four hours of incubation with respect to hatchability. Poultry Sci. 24: 414-419. Olsen, M. W., and S. J. Marsden, 1954. Mortality among turkey embryos in relation to rate of embryonic development. Poultry Sci. 33: 11461151. Olsen, M. W., 1956. Fowl pox vaccine associated with parthenogenesis in chicken and turkey eggs. Science, 124: 1078-1079. Payne, L., L. Ortman and P. B. Siegel, 1957. Early detection of fertility in turkey eggs in relation to "shuck-outs". Poultry Sci. 36: 576-579. Yao, T. S., and M. W. Olsen, 1955. Microscopic observations of parthenogenetic embryonic tissues from virgin turkey eggs. J. Heredity, 46: 133-134.
NEWS AND NOTES (Continued from page 1143) cal Society of America was formed, and this Section is now linked with the Association. An Associate Editor from the United States has been appointed as well as several members of the Editorial Board. In order to preserve continuity, the first volume of Animal Behaviour is numbered Volume VI. It is published twice a year in March and September at an annual subscription of 50 shillings. Manuscripts should be sent to The Editors, Animal Behavior, Nutritional Research Unit, Huntingdon, England, or in the case of contributions from
the United States to D. E. Davis, School of Hygiene and Public Health, Johns Hopkins University, Baltimore 5, Md. The Editor is A. N. Worden, with B. A. Cross (Cambridge) and D. E. Davis (Baltimore) as Associate Editors. The other members of the Editorial Board are L. R. Aronson (New York), J. D. Carthy (London), N. E. CoUias (Carbondale), J. T. Eayrs (Birmingham), A. E. Emerson (Chicago), J. T. Emlen (Madison), G. C. Grindley (Cambridge), E. B. Hale (University Park), John Hammond (Cambridge), L. H. Matthews (London), E. Hess
(Continued on page 1255)
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on April 18, 2015
Broad Breasted Bronze hatching eggs, stored 1-7 and 8-14 days prior to incubation, were first candled 36 hours following setting and then once daily for the next 5 days. 2,710 eggs were involved. The time-lag necessary for the initial in-shell detection of fertility was determined and related to hatchability. A higher proportion of the 1-7 day eggs showed a definite tendency to "start" development 36 hours after setting (as indicated by candling appearance) and to hatch better than did the 8-14 day eggs. Some of the latter showed no identifiable signs of development until the 156th postsetting hour. No eggs which had a timelag longer than 84 hours hatched. The hatchability of those 8-14 day eggs in which fertility could not be identified until 60 hours post setting was higher than that of the 1-7 day eggs. The frequency of retarded embryos was affected by pre-incubation treatment of eggs. Certain inferences are drawn from these observations with respect to the possible prevalence of parthenogenetic development in eggs from mated hens.
1153