Origin of Sexuality ^55 



exhaustively studied by algologists. But, even granting such, 

 we beheve that the above pretty surely represents the state 

 of the case. 



If such be so, it can be said that differentiation of the com- 

 plex chromatin substance, that is mainly centered within the 

 nucleus, and which we have regarded as a dehcately sensitive 

 mass for storage and distribution of cognitic energy (p. 129), 

 took place antecedently to the origin of sexuality. As will be 

 pointed out below the same seems to be true for animals. 



But it would be a mistake to suppose, as has often been 

 done in recent years, that sexuality arose after formation of 

 swarmspores, and in connection with their active movements. 

 For, in the large but comparatively primitive and wholly fresh- 

 water group of the Desmidese, the conjugating cells are ordi- 

 nary vegetative cells, which at definite periods undergo a 

 profound change in the chromatin, so as to start the conjugating 

 process. The Conjugatse generally and the Diatomacese also 

 conform to this. 



In nearly all the primitive unicellular and multicellular 

 caryote algae then, except those above named and others soon 

 to be cited, the formation of swarmspores is a general phe- 

 nomenon, though their production need not be followed by 

 sexual differentiation in them. Each swarm spore may rep- 

 resent the entire rounded-off contents of a cell, as in Oedo- 

 gonium, or the contents may divide again and again to produce 

 several swarmspores. In nearly every case, it may be said 

 that each stands in striking contrast to the cell that produced 

 it, in being greatly more sensitive to external stimuli. This is 

 shown first in the production of the cilia, which are often — 

 perhaps always — formed as prolongations of the chromatin or 

 cognitic substance. 



Further the cilia protrude from the clear and usually pointed 

 end of the spore, the posterior rounded green end of wliich 

 is evidently the more purely biotic or vegetative portion. The 

 cilia and soft anterior end then are readily ])ermeable by heat 

 and light rays, by chemical agents, and by currents of electric 

 or other energy, so that alike in character and in behavior it 



