


Igor ] CURRENT LITERATURE 445 
peculiar form of multiplication illustrated by Pediastrum and Hydrodictyon. 
This is essentially a method of spore-formation with the peculiarity that the 
zoospores, unable to escape from the sporangium, settle down to form a new 
individual within the mother cell. These three conditions have been recog- 
nized by several phycologists, and probably express the history of events fairly 
correctly for this region of the algae, where the original conditions and later 
modifying factors seem relatively clear. 
The Conjugales, Siphonales, and Diatomales form natural groups that 
cannot be closely related to the Protococcales or Confervales. They have 
not been treated in this paper, which deals chiefly with the Chlamydomonas- 
like organisms, flagellates, and a certain assemblage of forms termed the 
“‘Heterokontae.” It is doubtful whether most botanists realize that the 
immense group of the Flagellata resembles the lower Volvocales so closely 
that no hard and fast line can be drawn between them and the algae. This 
relationship is treated at some length, and should be welcomed. In his 
remarks upon the primitive Phaeophyceae Dr. Blackman enters a field of 
acknowledged difficulty, and while he presents certain possibilities the 
reader cannot but realize that he is speculating in a region where there is a 
conspicuous paucity of knowledge. 
The author of a paper of this character naturally lays himself open to 
criticism, for his is an attempt to connect and relate groups as definitely as 
possible with confessedly fragmentary evidence at hand. Certain difficulties 
are presented in this paper which cannot be easily overcome. Is not 
Chlamydomonas much too high a type on which to pivot so many evolutionary 
lines? What is to be done with the simplest of the Pleurococcaceae? There 
is little or no real evidence that they are degenerate forms, and this view 
seems to have its chief ~azson d’étre as an assumption to dispose of a trouble- 
some difficulty. Chlamydomonas is very complex as a cell, with its differ- 
entiated activities, sex, etc. There were, of course, immense stretches of 
simpler forms below this level, perhaps rising out of the Cyanophyceae. 
We know almost nothing of the cytology of the Pleurococcaceae, the Crypto- 
monadineae, and other border groups. It seems to the writer that we may 
hope for important results from this field of investigation. We shall probably 
have to go much farther back than Chlamydomonas before we can hope to 
clear the maze of relationships in the Pleurococcaceae.— B. M. Davis. 
