274 



THE AMERICAN NATURALIST [Vol. L 



The actual division of the chromatin takes place by the 

 longitudinal splitting of the chromoneme, in other words, 

 by simultaneous division into two of each of the chro- 

 mioles of which the thread is composed. In this way 

 every chromiole which was contained in the original 

 chromoneme is represented by a daughter-chromiole in 

 each of the two daughter-chromonemes. It follows that 

 the familiar process of the splitting of the chromosomes 

 in karyokinesis is a mechanism which brings about in the 

 most simple, sure and direct manner an exact quantita- 

 tive and qualitative partition of the chromatin-grains be- 

 tween the two daughter-nuclei. In the sequel each daugh- 

 ter-nucleus is built up, according to Vejdovsky-, entirely 

 and solely from one of the two daughter-clumps of chro- 

 mosomes, and each chromosome is resolved again into its 

 constituent chromioles, giving rise in some cases to a defi- 

 nite portion of the nucleus, a karyomere, from which 

 again, at the next nuclear division, the chromosome is 

 reconstituted by the chromioles falling into line in an 

 orderly manner. 



The chromatin-cycle of a cell in which the process of 

 division by karyokinesis takes place in its most perfectly 

 developed form, may, therefore, be conceived as follows : 

 The nucleus in its resting state contains a definite number of 

 companies or brigades of chromatinic units (chromioles), 

 each brigade spread over a certain extent of the nuclear 

 framework forming a karyomere. As a preparation to 

 division each separate brigade of chromioles falls into 

 line as the chromoneme, forming with its supporting sub- 

 stance the chromosome; there are formed, therefore, just 

 so many chromosomes as there were karyomeres in the 

 nucleus. In this disciplined and orderly array each chro- 

 miole undergoes its division into two daughter-chromioles, 

 so that each file or chromoneme of chromioles splits into 

 two files. At the reconstitution of the daughter-nuclei 

 each daughter-chromosome gives rise to a karyomere 

 again, the chromioles falling out of the ranks and dispos- 

 ing themselves in an apparently irregular manner on the 



