340 Causes and Course of Organic Evolution 



The changes subsequent to fertihzation, and that lead up 

 to formation of the alternating or sporophyte generation, are 

 at present by no means so easily explicable. Pringsheim and 

 Oltmanns have sho^Mi that in Coleochoete the fertilized egg 

 divides and redivides till 8 "octant cells" are formed. But, 

 if the chromosomic cell details of C. scutata have been correctly 

 interpreted, such might suggest that a very short-lived sporo- 

 phyte generation in it, that closes when division into octants 

 is about to occur, becomes extended in other species — as Lotzy 

 (119, 1: 193) has suggested — to include the group of 8 or in 

 some cases even 16 cells. 



If such be correct, and considerable evidence can be advanced 

 in favor of it, a more complex advance next toward Riccia 

 would be the formation from and around these 8-16 cells of 

 an enclosing wall-layer, the sporogonial wall. For it should 

 be noted that the zone of pseudoparenchyma formed round 

 the fertilized egg of C. pidvinaia is a purely accessory structure, 

 and even suggests, by its formation, the view that Coleochcete 

 is a surviving type along a lateral line of green algoid advance, 

 rather than along the direct pathway. 



In Riccia the fertilized egg divides and redivides to form 

 an octant mass, which by continued division in time gives 

 rise to a wall-layer and numerous enclosed spore cells, the whole 

 forming a subspherical mass inside the archegonium. 



Each of the 8-16 zygospores of Coleochoete, when mature, 

 bursts and sets free a biciliate swarmspore, that after a time 

 fixes do\Mi to form a tube or cylindric cell. Tliis then produces 

 a sexual or gametophytic plant at its extremity. But, in 

 passing through protoriccioid forms that frequented drier 

 surroundings, the germinating spore seems to have gradually 

 changed from a ciliate swarmspore condition to that of a non- 

 ciliate cylindric cell, that early fixed to a substratum by rhi- 

 zoids, and which constitutes the protonema of the hepatics 

 and mosses. This has remained as a simple cell in nearly 

 all of the Hepaticse, and even in Riccia the colorless rhizoids 

 that grow out from it do not become septated off by walls. 

 But the swarmspore or — as we would view it — the correspond- 



