270 MARGARET MORRIS HOSKINS. 



changes of form during the development of the egg. At first 

 sight, the evidence given in this paper seems to agree with 

 Jordan's conclusion. If the persistence or recurrence of a definite 

 group of chromosomes at each mitosis is essential to proving 

 them individuals, the bodies in Cumingia cannot be so designated, 

 since an entirely abnormal arrangement of the chromatin may be 

 substituted for the usual group without injury to the egg. This 

 use of the word "individuality" (implying unity and a separate, 

 definite existence) has been made by many writers, and has led 

 to much argument and confusion. It is not, however, the sense, 

 in which all supporters of the theory of the individuality of the 

 chromosomes have applied it. As McClung ('17) for instance, 

 uses it, it means that each chromosome is qualitatively different 

 from the others in the group "a single thing of a given kind." 

 The essential point is that the chromatin is "differentially 

 organized and linearly arranged," and the chromosomes are 

 aggregates of this substance, individual in the sense that they 

 have specific characters. This theory is broad enough so that 

 Hance's work (1918) really supports it. Hance finds, both in 

 (Enothera scintillans and in the pig, certain fragmented chromo- 

 somes. The parts of chromosomes behave like normal bodies 

 in the various stages of mitosis, and such facts would be in 

 opposition to the narrower view of the individuality of the chro- 

 mosomes. Hance, concludes "If the theory of the individuality 

 of the chromosomes can only recognize a strict morphological 

 continuity then the chromosomes in Scintillans lose their indi- 

 viduality through breaking up. If the theory is broader in its 

 scope and admits an individuality not only of whole chromo- 

 somes, but of the chromatin or chromomeres, the scintillans 

 situation falls within its limits." 



The conditions found in Cumingia give no information with 

 regard to the organization of the chromatin or the individuality 

 of chromomeres. All that can be established from them is that 

 the aggregation of the chromatin into definite bodies is subject 

 to a certain amount of variation under normal conditions, and to 

 very great alterations under the influence of heat. This behavior 

 is entirely consistent, so far as I can see, with the belief that the 

 chromatin is definitely organized and that the normal chromo- 



