. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 438 JOHN R. HARRISON and 15 or produced normal embryos. From this particular flock of chickens, fertile eggs develop normally for the first two days in better than 90% of the cases. In the second type 107 fertile eggs were incubated for 9 days at 25° C. followed by incubation for two days at ° C. Fifty-one of these () produced normal embryos. This potency for normal development was not as high as pre- viously reported (Harrison and Klein, 1954). In the earlier work one group of 10 eggs was pretreated for 10 da
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 438 JOHN R. HARRISON and 15 or produced normal embryos. From this particular flock of chickens, fertile eggs develop normally for the first two days in better than 90% of the cases. In the second type 107 fertile eggs were incubated for 9 days at 25° C. followed by incubation for two days at ° C. Fifty-one of these () produced normal embryos. This potency for normal development was not as high as pre- viously reported (Harrison and Klein, 1954). In the earlier work one group of 10 eggs was pretreated for 10 days at 25° C. Ninety per cent of the eggs produced normal embryos. In the present work, 11 groups of eggs were set, and the highest percentage of normal development for any group was and the lowest was normal development. The average of is comparable to that obtained in 1957 (Harrison) and is more indicative of the true developmental potency of eggs exposed at 25° C. and subsequently incubated at ° C. in ovo. The present control groups consisted of 5 to 26 eggs and represent a much better sampling than did the 1954 group. Differences between the groups, in terms of susceptibility to the low temperature exposure, seem to be the result of individual variations in eggs. AREA OPACA — AREA PELLUCIDA. VACUOLE PRIMITIVE STREAK I mm. FIGURE 1. Morphology of a typical diffuse streak blastoderm resulting from incubation for 9 days at 25° C. Variations in level of blastoderm transection To determine whether or not the amount of streak which remained in a transected blastoderm affected its in vitro development, a series of experiments was performed transecting the blastoderm at different levels of the primitive streak behind the node. In all instances the blastoderms used were those previously classified as "diffuse ; Figure 1 represents a typical diffuse streak blasto- derm. In general, the area pellucida tends to be elliptical rather than narr
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
