Origin of Sexuality 273 



the protoplasm to the periphery, while the nuclei are bounded 

 by a definite nuclear membrane, and show within either scat- 

 tered chromidia or an evident nucleolus, at times of elo agate 

 shape as in Tuscarora. 



In the Hsemoflagellata, according to Schaudinn and suc- 

 cessors, as development of a maturing trypanosome takes 

 place, the parent nucleus divides (p. 223) into a larger half 

 or trophonucleus that presides over the general vegetative 

 functions, and a smaller half that is largely hereditary and 

 irrito-reproductive. Tins again divides into a kinetonucleus 

 that directs movement, and an elongated portion that spreads 

 into the flagellum and the membrane. During division each 

 of these contributes daughter nuclei to the new cells. As will 

 be noted below the trophonucleus and kinetonucleus fuse, 

 previous to formation of gamete cells. 



The third group includes only the Infusoria, but these, in 

 the relation and distribution of the protoplasm and chromatin 

 materials, are as suggestive as they are complex. The appar- 

 ently homogeneous structure of the ectoplasm in some cases, 

 or division of it into as many as three layers in other cases, 

 the diverse functional nature of the latter, the extreme mo- 

 bility and yet correlated action (^^; 44) of the cilia, the detect- 

 able existence at times of a radiating endoplasmic reticulum 

 (JDendrocometes, etc.), the division of the chromatin into a 

 micronuclear and meganuclear constituent, as well as the size 

 and occasional branched nature of the latter in some genera 

 (e. g., Stentor, Ephelota, Opalinopsis), all indicate that this 

 group is not only the most specialized in protoplasmic and 

 chromatin substance amongst Protozoa, but that though uni- 

 cellular not a few of its members deserve to rank high along- 

 side many Metazoa, in morphological differentiation for phj'si- 

 ological work. 



With such details of protoplasmic and chromatin or nuclear 

 differentiation to hand, it may further be said that, as amongst 

 the simpler Algae, so also throughout the Protozoa, asexual 

 multiplication by division, by budding, and by free cell for- 

 mation or endogenous multiplication occur, while the redis- 



