Origin of Sexuality 271 



reserves of available energy are conveniently placed for the 

 future sex-cells so as still later to nourish the succeeding em- 

 bryo plant. ''Reduction division" however seems biologically 

 to be of prime importance in all interpretations of sex-history, 

 and so will receive detailed attention later. 



Sexuality in the Protozoa — We can pass next to studies in 

 cell-liistory and sexuality amongst the Protozoa. The entire 

 group, as now living, may conveniently be divided for our 

 present purposes into three series, that seem to show advancing 

 complexity in their cytological history. The first is made up 

 of the Rhizopoda, the fresh-water Foraminifera, the Heliozoa, 

 and the Sporozoa. The second consists of the marine Foramin- 

 ifera, the Radiolaria, and the Hgemoflagellata; the third of 

 the Infusoria. 



It seems increasingly problematical whether such a mor- 

 phological group as that of the Proteomyxa exists, of simpler 

 constitution than the higher Rhizopoda or Lobosa. But in 

 such genera as Leptophrys, Gymnophrys, and Protamoeba no 

 nucleus has been detected. In these and in most genera of 

 the Proteomyxa also, no conjugation act has been observed. 

 Here then, as amongst the Protophyta, the absence of a nucleus 

 and of sexual differentiation of cells seem to be associated 

 features. But the cell protoplasm is evidently so capable 

 of rejuvenescence in its molecular substance that it grows, 

 divides, and multiplies endogenously, as do many bacteria 

 and Cyanophycese. The variety of species and genera also 

 that have evolved in the past is again suggestion that non- 

 nucleate or semi-nucleate animals are capable of variation, 

 of hereditarily transmitting acquired variation characters, 

 and of fixing these to a greater or less degree, and for a longer 

 or shorter period, so as to constitute recognizable specific or 

 generic characters. 



The genera and species of the Lobosa vary in an interesting 

 manner, alike in the structure and distribution of the proto- 

 plasm or biotic substance, and of the chromatin or cognitic 

 substance. Thus in some cases the former may be soft, fluid, 

 and loosely alveolar in structure, while the latter is a spherical 



