THE ORIGIN OF VAKIATIONS 5.'5 



Which raises the natural c|iiery — Whence the addi- 

 tion ? The addition is the essence of the variation ; 

 it is the variation. Hence the last sentence quoted, 

 which professes to exphxin the cause of the variation, 

 does not seem to nie to fulfil its promise. Surely 

 when Mr. Reid wrote " It results from . . . ." he 

 meant " It consists in . . . ." 



If next we consult the admirable arti(;le on heredity 

 recently contributed by Professor Arthur Thomson to 

 the Encyclopaedia Medica, we find no discussion of 

 the cause of variations, save in so far as his cautious 

 rejection of the doctrine that acquirements are 

 transmitted {i.e. are causes of variation) answers to 

 this description. 



Next we may hopefully turn to the article, "Varia- 

 tion and Selection," recently written by Professor 

 Weldon for the new volumes of the Encyclopedia 

 Britannica. But again we are disappointed. True, 

 Professor Weldon cites the evidence which disproves 

 Weismann's theory that bi-parental reproduction is 

 the chief cause of variations ; but the only positive 

 statement as to the true cause of variation is that, 

 " the production of a regular series of variations, 

 under given environmental conditions, is a property 

 of species as constant as the production of typical 

 individuals." This is an exceedingly important 

 proposition, but it does not satisfy us who are scek- 

 iuLT to know the cause or causes of variations. The 

 author of the new article, "Embryology," in the same 

 work, who is no less a person than Hans Driesch, 

 inclines to the theory of Weismann. Dr. Chalmers 

 Mitchell, the author of the new article, " Evolu- 

 tion," clearly recognises the distinction between 



