134 D. H. WENRICH 



rounded-up kind, especially in material from hosts which had 

 been dead several hours. I have also seen in some hosts con- 

 siderable numbers of the contracted forms in the coecal contents. 

 In figure 36 I have represented one of these, and it is very similar 

 to the one figured by Wenyon. In figure 35 there is shown one 

 which is apparently in the process of changing to the rounded 

 and contracted condition. I am inclined to the belief that these 

 animals are preparing to encyst, since there is no sign of degenera- 

 tion except the apparent disappearance of the free flagella. 



DIVISION 



All authors who have studied carefully the division of any 

 of the species of Trichomonas agree that the process is compli- 

 cated and appears to take a relatively long time for its accom- 

 plishment. Kuczynski ('14) gives eight hours as the time for T. 

 augusta. It is also generally agreed that the flagellates remain 

 active during the entire process, the flagella and undulating 

 membrane continuing to vibrate even in the rounded-up con- 

 dition which is characteristically assumed during part of the 

 time. The extensive activities of the post mitotic phase have 

 been well described and illustrated for T. augusta by Kofoid 

 andSwezy ('15). 



Since it is possible to recognize in the division of the nucleus 

 stages comparable to those of mitosis in metazoan cells, it will 

 be convenient to refer to these stages under the conventional 

 terms, prophase, metaphase, anaphase, and telophase. 



A, Prophase 



1. The nucleus. The first changes in the nucleus which indi- 

 cate the approach of mitosis result in the formation of the pro- 

 phase chromosomes out of the scattered chromatin granules of 

 the 'resting' nucleus. There are always six of these chromo- 

 somes, and each one consists of a pair of closely associated 

 moieties. The parts are often somewhat elongated and the two 

 components lie side by side. These prophase elements remain 

 connected with each other and with the caryosome, until the 

 end of the prophase stage, by the fine strands of non-chromatin 



