62 Morphology BooK T 



they are not inconsistent with reasonable interpretation of 

 the facts recently observed. In particular, he objected to 

 the view of an intercalation of a new generation (the sporo- 

 phyte) in the course of a series. He said, ' If we are to 

 apply the antithetic theory of alternation to these cases 

 (Oedogonium and Coleochaete) we must assume that the 

 zoospores produced on germination in the oospore are a 

 new formation intercalated at this point of the life-cycle. 

 But is this assumption borne out by the facts ? I think 

 not. In reality nothing new is intercalated at all. The 

 zoospores formed from the oospore on germination are 

 identical with the so-called zoogonidia formed on the vege- 

 tative plant at all stages of its growth ... To my mind the 

 point seems to be this— an Oedogonium can form zoospores 

 at any stage of its development ; there is one particular 

 stage, however, at which they are always formed, viz. on 

 the germination of the oospore. Nothing new is inter- 

 calated, but the irregular and indefinite succession of sexual 

 and asexual acts of reproduction is here tending to become 

 regular and definite.' 



The homologous theory received some support in 1896, 

 and later in 1898, by Lang's discovery of the occurrence of 

 well-developed sporangia on the prothallus of a species of 

 Lastrea. This was interpreted, as had previously been the 

 phenomena of apospory and apogamy, as indicating that 

 the prothallus and the fern plant are fundamentally 

 homologous. 



It was contended, on the other hand, by the advocates of 

 antithetic alternation that all these phenomena are tet-ato- 

 logical, and therefore no conclusions on an important 

 question of this kind can fairly be drawn from them. 



Towards the end of the century Klebs published the 

 results of his experiments on the influence of the environ- 

 ment in modifying the reproductive processes. His work 

 was carried out mainly on the green Algae, and went to 



