10 Professor Gregg Witsoii on 



the formation of a female with fourteen chromosomes in its cells, 

 and in every cell two are of the large type. Much evidence of 

 this nature goes to show that sex is determined just as the 

 Mendelian greenness or yellowness in peas are inherited. 



The Darwin- Weismann school certainly is mechanistic in 

 tendency. Its extreme disciples regard all nature as the necessary 

 result of the " mutual interaction, according to definite laws, of 

 the forces possessed by the molecules of which the primitive 

 nebulosity of the universe was composed."* The present is an 

 unfolding of the past, and the future is a certainty, and is 

 determined by the present. The development of the individual 

 is a mere displaying of characters contributed by the parents to 

 the egg; but these characters depend for survival und unfolding 

 on environmental conditions, such as nourishment, temperature, 

 &c. Similarly the evolution of the race is an outcome of com- 

 binations of characters, fostered by natural selection. Even 

 psychical qualities are given a mechanistic interpretation : for 

 example, Loeb says : "I consider consciousness the function of a 

 definite machine or mechanism, which we may call the mechanism 

 of associative memory."! 



Weismann found many followers, especially, perhaps, in 

 Britain ; but there were always many zoologists who had difficulty 

 in accepting the rigidly mechanical account of the germ-plasm 

 associated with his name ; and others were unwilling to give up 

 belief in the old doctrine of transmission of acquired characters. 

 This century seems to me to be specially marked by the 

 perception of difficulties in the mechanistic view, and by a 

 tendency to a revival of Lamarkism or other form of vitalism. + 

 The first adverse criticism of the " Natural Selection " 

 school that I would mention refers to the casual variations, which 



* Huxley. 



tProfessor J. Loeb: " The Dynamics of Living Matter." 190G. page 6. 



J The notes that follow are not put forAvard as a i-easoned criticism of 

 the mechanistic school, but rather as jottings indicating generally the 

 nature of some of the difficulties felt with regard to its teachings, and some 

 of the recent suggestions that are on vitalistic lines. 



