254 Causes and Course of Organic Evolution 



So it seems to the writer that the bulk of evidence is in favor 

 of the position that the different types of asexual reproduction 

 and spore-cell formation had already evolved amongst the 

 Cyanophycese, and that as chromatin organization became 

 perfected the swarmspores originated, that represent not merely 

 the structural details and functional capabilities of a biotic 

 energy, but the much more speciahzed phase of cognitic energy. 



Now, as shedding a certain light on evolving sexuality, it 

 is important to note that all of these asexually produced spore 

 cells are capable of exactly reproducing the type or species of adult 

 plant from which they have been derived. And this holds true, 

 not only for the nucleate algse that we are now considering, 

 but equally for all of the non-nucleate or semi-nucleate blue-green 

 genera. So every vegetative cell which becomes a potential 

 spore-cell — and in many cases, as Radaisia and Hyella amongst 

 Cyanophycese, or Stigeoclonium and Ctenocladus amongst green 

 algae, such make up the bulk of the plant at certain seasons — 

 has the potentialities and energizing tendencies locked up in 

 it which enable it to reproduce the adult form, and this in 

 turn to reproduce the varied kinds of spore — akinete, aplano- 

 spore, or zoospore — characteristic of the species. 



We shall now attempt to ascertain how sexual differentiation 

 gradually arose amongst the lower nucleate algae. 



According to our present knowledge of their life histories, 

 it can be said that many living genera amongst some of the 

 simplest nucleate green algae are invariably characterized by 

 the formation of swarmspores, but these neither become sexual 

 gametes to conjugate with each other, nor are sex-cells formed 

 at any stage in the history of the genera. Thus the Pleuro- 

 coccaceae and Protococcaceae that we would regard as most 

 directly derived from unicellular Cyanoi)hyceae (p. 308) have 

 hitherto failed to show sex-cells in the thirty or more genera 

 that make Mp the groups, except in a few like Chlorochytrium 

 and Endosphcera. Many even of the Pleurococcaceae fail to 

 form swarmspores, and multiply only by such methods as 

 are seen in the Cyanophyceae. A considerable margin of 

 doubt however must attach to these, till they have all been 



