1922] Klugh,—Polymorphism in Enteromorpha crinita 51 
those who have dealt with the subject, may be defined as the ability 
of an organism to exist in two or more different forms and to repro- 
duce in each of these states, such states not being phases of the ordi- 
nary life-history of the species, and this is the sense in which the term 
is used here. . 
Very wide polymorphism transcending the limits not only of 
species and genera but of orders, classes and phyla has been proclaimed 
by some writers. Thus Metcalf Johnson (’71) maintained that a 
Paramoecium could give rise to a Vorticella and this to an entomostra- 
can, and a Monas to a Chlorococcum and this in turn to an Oscillatoria, 
a moss or a lichen. Such ideas hardly call for comment nowadays. 
The idea of polymorphism in the algae was first put forward by 
C. A. Agardh in 1829, and Kützing (40), Borzi (83) and especially 
Hansgirg (85) claimed that most of the Cyanophyceae and Chloro- 
phyceae were polymorphic and that the simpler forms of these 
groups were only developmental stages of higher forms. These as- 
sertions were based on insufficient data and subsequent experimental 
work has shown that they were far too sweeping, so that the tendency 
among modern authorities, for example Klebs ('96), Chodat (09) and 
West (716) is to relegate polymorphism to a very minor position in algo- 
logical considerations. Nevertheless, while the algae as a class may 
not exhibit any greater tendency towards polymorphism than some 
other groups of organisms, there are many well-substantiated cases 
of polymorphism in this class as is shown by the work of Goroschan- 
kin (91) on Chlamydomonas, Cienkowski ('76) and Livingston (’00) 
on Stigeoclonium, Gay (791) on Ulothrix, Chodat and Malinesco (793) 
on Scenedesmus acutus, Huber (794) on Chactonema irregulare, Senn 
(99) on Coelastrum microporum, Chodat (’09) on Heterococcus viridis 
and Rayss (15) on Coelastrum proboscideum. 
While we cannot enter here into a discussion of polymorphism in 
other groups of organisms it is of interest to notice that its occur- 
rence in bacteria is shown by many workers (See Hiss and Zinnser, 
'16 and Reed, ’22), in Amocba by Hausman (’20), in the rotifer Brach- 
ionus by Whitney (16), in Gastropoda by various investigators, in 
Daphnia by Stingeln (797), in Hyalodaphnia by Zacharias (703), in 
the scale-insect Leucanium by Marchal ('08), in the moth Porthretria 
by Pictet (705), in trout and sticklebacks by Jordan, and in sala- 
manders by several workers. 
