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THE AMERICAN NATURALIST [Vol.XLIV 



We doubt whether some of the conclusions reached, in regard 

 to the causal nature of the various chemicals used in the differ- 

 ent cultures in producing oogonia and other changes in certain 

 of the species studied, should be accepted without further study 

 and more conclusive evidence. The author says: "The results so 

 far indicated show that it is possible to produce, where hitherto 

 they were believed to be absent, antheridial branches of the 

 normal type known in other species of the family, and that their 

 production is conditioned by the presence of definite inorganic 

 salts." The fact that antheridial branches appeared quite con- 

 stantly in cultures containing certain inorganic salts, does not, 

 in our opinion, necessarily prove that their occurrence was due 

 entirely to the action of such salts. In order to make such a 

 conclusion justifiable, it would be necessary, at least, to carry 

 on a very long series of cultures, covering many generations of 

 pedigreed forms originating from different individuals of the 

 organism under investigation, to say nothing of other possible 

 factors which may be unknown. It seems probable from recent 

 investigations by Miss Wakefield 2 and others that there are fer- 

 tile and sterile races or strains of species which differ in no other 

 respect from each other and apparently do not depend upon 

 the presence of any particular inorganic salt. An organism re- 

 produced vegetatively would also presumably tend to be more 

 constant in its behavior and show less variation than when each 

 new generation was produced from spores. 



Our studies of pedigreed strains of many generations of 

 GUrosporium and CoUetotrichum started from single spores lead 

 us to the conclusion that there are some other factors or forces 

 involved in the variations which occur in different generations 

 from single spores which have no perceivable connection, so far 

 as yet determined, with the composition of the medium in which 

 they grow. Apparently spontaneous variations appear in such 

 series of generations at the most unexpected moment under ap- 

 parently identical conditions of environment and culture media. 

 We say apparently because it is probably beyond our power at 

 present to determine much less to control all the factors con- 

 cerned in the growth and behavior of an organism. 



