INDIVIDUALITY OF CHROMOSOMES. I/ 



That the shape is not a mere happening so, a ring now, and a 

 cross then, is met, in part at least, by the probability of the con- 

 stancy of the number of rings found in the various cells. I could 

 see no way of testing the constancy of the other forms, such as 

 the cross. 



Taking all these observations into consideration it seems to me 

 the best hypothesis that we can propose to explain the various 

 forms assumed by the chromosomes in the prophases and meta- 

 phase of the first spermatocyte is to say that these various shapes 

 are an expression of the individual characteristics of the various 

 chromosomes. They are a proof of the individuality of the chro- 

 mosomes. I would repeat in the way of emphasis that Boveri 

 has found a difference in function, Sutton a difference in size and 

 I a difference inform in the chromosomes of the germ cells. 



That these observations will be found to have a wider applica- 

 tion I would predict from the many indications I find in literature 

 especially the results on Ascaris. But in many species as in G. 

 assimilis the form of the chromosomes is not varied enough to 

 establish a constancy of any one form, just as size differences can 

 probably not be found in all species. Some other species will 

 probably prove much better to establish morphological differences 

 in the chromosomes than G. domesticus ; yet I consider this ma- 

 terial very good for the purpose. I trust that other workers who 

 find a great variety of chromosome shapes will examine their 

 material from this view point. 



That the hypothesis, or theory as Boveri (6) would call it, has 

 received an unfortunate name Wilson points out in his "Cell," 

 p. 299. But I do not believe that many cytologists think that 

 chromosomes persist as individuals. Nor do I believe that we 

 generally think of a " continuity of the chromatic substance " 

 as Haecker (13) supposes (see page 217). Nor is he the first to 

 suggest that the continuity may rest upon the achromatic sub- 

 stance as shown in the quotation below. 



This passage quoted from Boveri (4) I think gives an idea of 

 what the advocates of the hypothesis mean by the individuality 

 of the chromosomes. " Ich habe dieselbe als die Hypothese 

 von der Individualitat der Chromosomen bezeichnet, weil die 

 Gebilde, die wir als selbststandige Stiicke kennen, den Namen 



