Phytogeny of Volvoeinese 



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

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

 the vegetative units of which arc far more primitive than those constituting the ccenobia of 

 Caelastrum, Sorastrum, or Pcdiastrum. 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 Vaucheria 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 Stephanosphsera in the Sphserellacese and 



TETRASPORINE/E 



A PALM ELL AC E^E 



VOLVOCINE/R 



Stephanoaphsera 



Sphaerella 

 ? Chlorogonium 



Eudorina 



Brachiomonas 



(Ionium 



Lobomonns 

 Agloo 



Pandorina 



Spondylomorura 



/ Phacotus I 



/ _ Scherffeha 



Pteromonas' 



Cartcria. 



TetrabFepharis 



Dunaliella 

 Stcphanoptera" C h!orast,er 

 Pyramimonas 

 ^Polyblepharides 



FLAG ELL ATA 

 (Protomastigina) 



nothing beyond Spondylomornin in the Carterieae, the cell-grouping in these 

 types being biologically unsatisfactory. 



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

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

 Spha&relln (= Hs&matococcus) and Stephanosphs&ra were such that they 



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