174 Algae. 



polymorphists, Hansgirg and Borzi, did not use the method of 

 pure cultures, and that Chodat, who began his work with cultu- 

 res that were not pure, modified his views considerably when he 

 did appl}^ this method. His latest extensive monograph deals largely 

 with the variations in the cell that can be caused by changes in the 

 culture medium. He concludes that there are certain algae which 

 by their extreme variability merit the name polymorphs, if by this 

 term one wishes to imply that a plant can present several different 

 phases without changing its nature. Consequently one is able to 

 some extent to defend the thesis that algae are Polymorphie. But 

 their polymorphism is of the same order as that shown by many 

 of the higher plants. As in the higher plants there are some that 

 are quite plastic and others less so. 



Lotsy has proposed the term Biaiometamorphosis to cover 

 thosc cases in which the form changes as a result of changes in 

 external conditions; the variations in Scenedesmus acutus described 

 by Grintzesco being a case of this type. To the author's mind the 

 term, althrough cumbersome, is better than polymorphism, since 

 this term has been used by many authors in many different senses. 

 The latest view of Chodat is more a concept of Biaiometamorphism 

 than polymorphism. 



In the biaiometamorphic results observed in the author's 

 unialgal cultures, there has been little change in the cellular rela- 

 tionships but a considerable change in the structure of the indivi- 

 dual cells. The variations occurring in the arrangement of the cells 

 are chiefly dependant on the variations in the manner of cleavage 

 of the mother cells. In the cells, in which the autospores are not 

 motile, or only slightly so, [Tetracoccus, Coelastvum, Scenedesmus 

 and Tetradesmus) there is a marked influence in the Variation of 

 the cleavage of the mother cell on the positions of the cells in the 

 coenobe. When the autospores are motile {Pediastrum) there is little 

 influence in the manncr of cleavage of the mother cell on the ar- 

 rangement of the cells in the colony, but the variations in the cel- 

 lular arrangement are largely biaiometamorphic. 



The fact that these variations are not uniformly present in all 

 of the colonies.of a culture shows that a distinction should be made 

 between variations in the external environment and changes in 

 internal conditions of the cell. Possibly it would be better to distin- 

 guish between internal and external biaiometamorphosis. External 

 conditions can be varied but the internal conditions cannot be con- 

 trolled and when variations are laid to changes in internal condi- 

 tions we are using a phrase which gives us absolutely no concept 

 of the actual processes involved. 



Since there is this great divergence in different coenobia that 

 are all descendants of a Single cell and which, at least in a liquid 

 medium, have been kept under the same conditions of temperature, 

 light, and chemical environment we must say that a greater impor- 

 tance must be attached to internal than to external conditions. The 

 internal conditions in the cell are constantly changing and as a 

 result the four cells formed from a Single mother cell are not alike 

 in internal condition and the colonies formed are not wholly alike. 

 It is this constant change in the cell that is the main cause for 

 whatever Variation occurs in the process of reproduction. 



The author's general results are summarized as follows: 



The arrangement of the cells in coenobic algae may be classi- 

 fied according to the relationships of th? cell axes. 



