9 g BIOLOGICAL LECTURES. 



that phylogenic inheritance is extremely slow in a state of 

 nature. 



It is desirable to establish non-infectious experimentation 

 involving the conditions named above, mainly as a test of 

 Lamarck's factor. Varigny has also proposed a crucial experi- 

 mental series mainly upon Buffon's factor. His volume upon 

 Experimental Evolution is an invaluable review, especially of 

 French researches in experimental transformism. Much of 

 this is in the line brought together some years ago by Semper 

 in his Animal Life. Varigny draws a valid distinction between 

 morphological variation and physiological variation, including 

 under the latter internal chemical and constitutional differences 

 which are not displayed in structure but must underlie all 

 reactions. Under the head of what I have called Gonagenic 

 Variation, the author discusses the work of Gautier * upon the 

 influence of previous fertilization in plants as well as upon the 

 chemistry of plants in connection with color variation. He 

 adds to the observations of Yung and Born other studies upon 

 sex determination. He describes the experimental teratogeny 

 or embryonic variation of Dareste, Fallou, and later observers. 



Throughout Varigny 's volume it is nevertheless evident that 

 none of the studies upon Ontogenic Variation hitherto have been 

 specifically directed to the vital problem, as they must be in 

 the future. Varigny makes a useful suggestion as to the 

 importance of imitating natural conditions in experimental 

 work, but he fails to emphasize the importance of the tests 

 set forth above in order to ascertain whether the acquired 

 modifications have actually been impressed upon the hereditary 

 mechanism or merely upon the various stages of ontogeny. 



The general conclusion we reach from a survey of the whole 

 field is, that for Buffon's and Lamarck's factors we have no 

 theory of Heredity, while the original Darwin factor, or Neo- 

 Darwinism, offers an inadequate explanation of Evolution. If 

 acquired variations are transmitted, there must be therefore 



1 Armand Gautier: Du Mecanisme de la Variation des Etres vivants. (Hom- 

 mage a Monsieur Chevreul a 1'Occasion de son Centennaire. F. Alcan. Paris. 

 1886.) 



