94 MOORE— MOST PRIMITIVE LIVING REPRESENTATIVE [April 24, 



conditions as recognized at the present time, they are essentially those 

 pointed out by Chodat, namely : 



1. A tendency towards the aggregation of motile vegetative cells, 

 with a gradually larger and more specialized motile colony. This is 

 the Volvox type and in no place in the plant kingdom do we have 

 a more perfect series of development than from the simple Chlamy- 

 domonas form to the complex and highly differentiated Volvox type. 



2. A tendency towards the formation of an aggregation of non- 

 motile cells into a filament or tissue by the repeated vegetative 

 division of an original mother cell. This is the Tetraspora type. 



3. The Endosphccra type, where the tendency towards the forma- 

 tion of vegetative divisions and septate cell formation is reduced to 

 a minimum. This is, of course, Chodat's sporangmm tendency, 

 although not so much importance is attached to it. 



Without going into details it may be said that various species of 

 Chlamydomonas (of which there are about thirty, all remarkably 

 constant as regards their cytological characters), taken collectively, 

 exhibit all these three tendencies and that the simpler forms of algas 

 which possess but a single tendency, seem clearly to have diverged 

 from some one species of this genus. 



The endosphserine tendency in Chlamydomonas has given rise 

 to a single family, Endosphcura, This is naturally strictly unicel- 

 lular and with no vegetative divisions ; the reproduction of the 

 species can take place only by the formation of zoospores or gametes. 

 A family so restricted as to its vegetative habit could hardly be 

 expected to develop very far and it is interesting to note that prac- 

 tically all the genera are epiphytic upon other algse or aquatic plants, 

 and that this habit of life has undoubtedly given rise to a distinct 

 group of fungi. The suggestion has been made that the peculiar 

 Siphonales may have developed from this Endosphcura type, and 

 while such a view is reasonable, it must necessarily, at the present 

 time, be a mere matter of speculation. 



But one family, the Volvocacese, has resulted from the develop- 

 ment of the volvocine tendency. While the evolution of sex in this 

 group has been carried to the highest possible degree, the restric- 

 tions of an enforced motile vegetative condition did not permit this 

 family to give rise to anything further. 



