Polymorphism 145 



POLYMORPHISM. Concerning the so-called ' polymorphism ' in the 

 Chlorophycese there has been written quite a considerable algological litera- 

 ture, much of which consists of records of superficial and inaccurate observa- 

 tions, accompanied by expressions of opinion based upon defective evidence. 

 Polymorphism, by which is meant the occurrence in nature of several different 

 alternative vegetative forms of one and the same species, occurs to a very 

 much less extent in the Algae than has been so persistently advocated by 

 some authors. 



Hansgirg, Wolle, Borzi, and others, have stated at different times that 

 there is a very wide polymorphism among Green Algae, that most of the 

 lower types are merely stages in the life-histories of the higher types, and 

 that many of the ' genera ' of the Protococcales are merely the polymorphic 

 forms of one Alga. Chodat, also, in his earlier essays, was a believer in 

 wide polymorphism among many Green Algae. Most of these statements 

 are assumptions which are not supported in any way by modern scientific 

 evidence, and they have in a large measure been due to misjudgment and 

 lack of precise methods of investigation. The evidence rested in nearly 

 every case on the occurrence together in one habitat, perhaps even in one 

 matrix, of many different Algse in various stages of growth 1 . There is a great 

 similarity between the various stages of closely allied species, and sometimes 

 between certain stages of widely separated species, and since they may be 

 all commingled in one stratum or mass, very exact methods are required to 

 unravel the separate life-histories. 



In the natural state, many of the unicells almost invariably live inter- 

 mingled with others; but because the physiological conditions of this 

 associate life appear to be necessary for their existence, it does not follow 

 that they are merely forms of one another, even if fancied intermediate 

 states have been recorded 2 . 



It is more especially the methods of pure culture followed out by Klebs and 

 his pupils, by Beijerinck ('90 ; '93), Grintzesco ('02), and later by Chodat 

 ('02 ; '09 ; '13), that have given the false hypothesis of wide polymorphism 

 its death-blow; although it must not be overlooked that exact observations 

 of the living Algae under natural conditions were equally against the theory 

 of wide polymorphism (Archer '62 ; G. S. W. '99 ; '04). The methods of pure 

 culture simply clinched the arguments for the stability of algal species. Pure 



i See also p. 30. 



3 The most recent advocate of the doctrine of wide polymorphism is Playfair, who in a paper 

 entitled ' Polymorphism and life-history in the Desmidiaceae ' (Proc. Linn. Soc. N. S. Wales, 

 xxxv, 1910) has put forward ideas regarding the wide Polymorphism of Desmids which are in 

 entire disagreement with all biological principles. The value of his statements may be judged 

 by his remarks on the Peridinieae, Flagellata, etc., concerning which he makes assertions which 

 are contrary to all the known biological facts relating to these organisms assertions which have 

 repeatedly been proved to be fallacious by the careful work of numerous investigators. 



W. A. 10 



