38 



THE AMERICAN NATURALIST [Vol. L 



bilities of chromatin-particles not concentrated or organ- 

 ized. Arcella would appear to be a very suitable form for 

 such investigations. This is a point to which my atten- 

 tion was drawn by my late friend Mr. C. H. Martin, who 

 has lost his life in his country's service. 



I have mentioned already in my introductory remarks 

 that the only reliable test of chromatin is its behavior, 

 and the whole of modern cytological investigation bears 

 witness to the fact that the chromatinic particles exhibit 

 the characteristic property of living things generally, 

 namely, individualization combined with specific behavior. 

 In every cell-generation in the bodies of ordinary animals 

 and plants the chromatin-elements make their appearance 

 in the form of a group of chromosomes, not only constant 

 in number for each species, but often exhibiting such defi- 

 nite characteristics of size and form, that particular, indi- 

 vidual chromosomes can be recognized and identified in 

 each group throughout the whole life-cycle. Each chromo- 

 some is to be regarded as an aggregate composed of a 

 series of minute chromatinic granules or chromioles, a 

 point which I shall discuss further presently. Most stri- 

 king examples of the individualization of chromosomes 

 have been made known recently by Dobell and Jameson 21 

 in Protozoa. Thus in the Coccidian genus Aggregata six 

 chromosomes appear at every cell-generation, each differ- 

 ing constantly in length if in the extended form, or in bulk 

 if in the contracted form, so that each of the six chromo- 

 somes can be recognized and denoted by one of the letters 

 a to / at each appearance, a being the longest and / the 

 shortest. 



(To be continued.) 

 nProc. Boy. Soc. (B), Vol. 89. (In the press.) 



