HISTORY OF CHROMOSOMAL VESICLES IN FUNDULUS. 



follows: 'The question whether the individual chromosomes 

 persist through the resting stage so that upon the resolution of 

 the reticulum into the chromosomes the same component chroma- 

 tin granules again go together to make the same chromosomes 

 from which they were derived is a question first raised by Rabl 

 and later definitely stated by Boveri. Since that time so much 

 evidence has accumulated to support this conclusion that it has 

 come to be rather generally accepted. Even a general review 

 of the evidence is unnecessary here. Such a review would show 

 that the fact has never been definitely demonstrated. Some of 

 the most direct evidences yet given are the observations of Herla 

 and Zoja on the Ascaris hybrids in which it was shown that the 

 small chromosomes of the variety univalens which entered the 

 resting nucleus with the larger ones of the variety bivalens again 

 emerged in characteristic form. Equally strong evidence is now 

 afforded by my observations on hybrid fishes. Here, as in the 

 Ascaris hybrid, two kinds of chromosomes enter the resting 

 nucleus from which each kind again emerges. As long as the 

 two kinds remain grouped, as during the two divisions, this fact 

 has little added significance, since within each group it would be 

 perfectly possible for the component chromosomes to exchange 

 chromatin granules during the resting period. If, however, as 

 occurs in the later cleavages, the two kinds of chromosomes 

 become mingled the chromatin granules of both kinds must lie 

 mingled together within the resting nucleus. If from a nucleus 

 the two kinds again emerge, it amounts almost to a demon- 

 stration that the chromatin substance of a given chromosome 

 forms a unit and that the unit persists." 



The evidence presented by Conklin and by Moenkhaus most 

 nearly touches the subject of my investigation of any that I have 

 found in the literature. Both of these workers failed to see in 

 their material that the chromosomes may actually be discerned 

 in the nuclei during rest as distinct vesicles. Yet both believed 

 that a continuity of structure does exist and that the chromo- 

 somes form persistent, independent units. My material offers 

 more complete and direct evidence that the vesicles persist and 

 leaves little room for doubt that the conclusion of the observers 

 mentioned is the correct one. 



