132 THE CANADIAN NATURALIST. [June 



causes which are alleged to produce the transmutation of species. 



Leaving out of the account many fanciful and untenable 

 hypotheses, both ancient and modern, we may notice : — (1) The 

 Lamarckian theory of Appetency ; (2) The Darwinian theory of 

 Natural Selection ; (3) The Owenian doctrine of " Innate 

 tendency to deviate from parental type;" (4) The doctrine 

 of arrested or advanced embryonic development ; — with the view of 

 ascertaining how far these several hypotheses may be employed 

 to account for observed facts. 



(1.) The Lamarckian theory is essentially that of effort in 

 certain directions giving power in those directions, and conse- 

 quently altering organs. That it has a real basis in nature 

 no one can doubt who has observed the effect of use and effort in 

 determining the development of organs. That it can produce 

 only varietal forms and not species, and that it is practically very 

 limited in its operation, are facts equally patent. It is a mis- 

 take, however, to suppose that Lamarck confined himself to the 

 effect of will in producing change. He considered also the 

 effect of external circumstances, and of habits induced by such 

 circumstances, in which respect his theory differed less than is 

 generally supposed from that of Mr. Darwin. The main 

 difference is, that Lamarck supposed auimals to be acted on by 

 an attractive influence from before, Darwin by a propelling 

 influence from behind. In this respect Lamarck's hypothesis is 

 the more philosophical, when regarded as means of real progress ; 

 but it is less applicable to the lower animals and to plants than to 

 animals of high grade. 



(2.) The most popular theory of derivation in the present day is 

 undoubtedly that of Darwin. This view is, essentially, that all 

 organized beings are engaged in a struggle for existence ; that in 

 this struggle certain varieties arise, which, being more suited to 

 the conditions, prosper and multiply more than others ; that this 

 amounts to a " Natural Selection " similar in kind to the artificial 

 selection of breeders of stock ; that members of the same species, 

 isolated from each other and subjected to struggles of different 

 kinds, will in process of time become specifically distinct. The 

 difliculties of Darwinism are many. The following may be stated 

 as fatal to it in its capacity of a sole mode of accounting for 

 derivation : — (1) Conditions which involve a struggle for 

 existence are found by experience to result in deterioration and 

 final extinction rather than improvement, and are directly op- 



