1200 Wisconsin Academy of Sciences , Arts and Letters. 
genus to another, has been more and more restricted until the 
recent polymorphists believe that- this variation is confined to 
a few species. The change in the concept of polymorphism 
has been due to more accurate methods of study, notable the 
application of the pure culture methods first used by Beyer inch 
(5). It is noteworthy that the most aggressive of the modern 
polymorphists, Hansgirg (19) and Borzi (6), did not use the 
method of pure cultures, and that Chodat, who began his work 
with cultures that were not pure (10) (13) (14), modified his 
views considerably (9) when he did apply 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 (p. 165) 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 
polymorphic. But their polymorphism is 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 (30) has proposed (p. 177) the term Biaiometamor- 
phosis to cover those cases in which the form changes as a re¬ 
sult of changes in external conditions; the variations in Seen &- 
desmus acutus described by Grintzesco (17) being a case of 
this type. To my mind the term, although cumbersome, is 
l etter than polymorphism, since the term has been used by 
many authors in many different senses. The latest view of 
Chodat (9) is more a concept of Biaiometamorphism than poly¬ 
morphism. 
In the biaiometamorphic results observed in my unialgal cul¬ 
tures, there has been little change in the cellular relationships 
but a considerable change in the structure of the individual 
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 auto- 
spores are not motile, or only slightly so. (Tetracoccus, Coelas- 
trum, Scenedesmus and Tetradesmus) there is a marked influ- 
