Phylogeny of Volvocinede 



1H3 



almost unique : but even Volvox, which is the culminating form of the scries, can hardly 

 be considered as having emerged from the Protococcales. It is still but a fragile colony, 

 the vegetative units of which are far more primitive than those constituting the coenobia of 

 Caslastrum, Sorastrum, or Pediastrmn. The high degree of differentiation of the gametes 

 in the higher forms, resulting in passive oospheres of large size and active antherozoids of 

 small size, is paralleled by the similar degree of sexual differentiation which has arisen in 

 several families of the Ulotrichales, and in Vauclieria among the Siphonales. 



Although there have been three attempts at the formation of coenobia 

 within the Volvocinese, each along a different line, that through Pandorina 

 and Eudorina has apparently been the only successful one. Nothing appears 

 to have been developed beyond Stephanosph&ra in the Spha3rellacese and 



TETRASPORINE/E 

 PALMELLACE^E 



FLAG ELL ATA 

 (Protomastigina) 



nothing beyond Spoil dylomorum in the Carterieae, the cell-grouping in these 

 types being biologically unsatisfactory. 



One of the most important of recent suggestions concerning the Vol- 

 vocineae was made by Schmidle ('03), who showed that the affinities between 

 Sphtvrella (= Hfematococcus} and Stephanos phwr a were such that they 



112 



