HISTORY OF CHROMOSOMAL VESICLES IN FUNDULUS. 26j 



Fig. 27 really represents the male and female halves of the 

 nucleus. That this is not the case, however, is shown by Fig. 28 

 in which only the Fundulus chromosomes are visible. Miss 

 Morris found that in Fundulus cytoplasm the Ctenolabrus 

 chromosomes are small round bodies, distinctly differentiated 

 from those of Fundulus. This observation I can corroborate; 

 the cytoplasm modifies the character of the foreign chromosomes, 

 and they can be recognized as different from those of the egg. 

 The egg from which these four figures were drawn was fertilized 

 with Ctenolabrus sperm that had been subjected to X-radiation 

 for fifteen minutes; this is sufficient duration of time for the 

 radiation to kill the male chromatin, which therefore made no 

 contribution to the development of the egg and is not repre- 

 sented, as is shown by Fig. 28 which contains only Fundulus 

 chromosomes. Since there is no male contribution to this 

 nucleus, the interpretation that Fig. 27 shows merely the male 

 and female halves of the nucleus is not valid. Rather the true 

 state of affairs is made clear by Fig. 29 which is a cross-section 

 of such a nucleus as is shown in Fig. 27; the central spindle 

 makes its way through the groove shown on the upper side of 



the nucleus. 



DISCUSSION. 



(a) Chromosomal Vesicles. 



While there are numerous cases cited in the literature which 

 would seem to give the conception of the constitution of chromo- 

 somes and resting nuclei here set forth a fairly wide application, 

 the writer does not care to attempt a generalization from these 

 observations extending the principle to other forms, although 

 some of the cases which support these findings must be given. 

 Any generalization at this time would seem unwarranted for 

 too many instances are known where neither the chromosomes 

 nor the chromatin during rest seem to answer exactly to these 

 descriptions. There are many cases, for example, in which the 

 chromosomes, judging from their behavior in the prophases, may 

 be regarded as made up in chromatin granules strung upon a 

 linin thread, and it is even possible to identify the granules in 

 homologous chromosomes. How such a structure is to be derived 

 from a permanent vesicular chromosome is not yet clear, al- 



