THE PACTOES OF ORGANIC EVOLUTION. 27 



or parts; and it is difficult in many cases to find such 

 arrangements, troublesome to maintain them even for one 

 generation, and still more through successive generations. 



Nor is this all. There exist stimuli to inquiry in the one 

 case which do not exist in the other. The money-interest 

 and the interest of the fancier, acting now separately and 

 now together, have prompted multitudinous individuals to 

 make experiments which have brought out clear evidence 

 that fortuitous variations are inherited. The cattle-breeders 

 who profit by producing certain shapes and qualities ; the 

 keepers of pet animals who take pride in the perfections 

 of those they have bred; the florists, professional and 

 amateur, who obtain new varieties and take prizes ; form a 

 body of men who furnish naturalists with countless of the 

 required proofs. But there is no such body of men, led 

 either by pecuniary interest or the interest of a hobby, to 

 ascertain by experiments whether the effects of use and 

 disuse are inheritable. 



Thus, then, there are amply sufficient reasons why there 

 is a great deal of direct evidence in the one case and but 

 little in the other : such little being that which comes out 

 incidentally. Let us look at what there is of it. 



Considerable weight attaches to a fact which Brown- 

 Sequard discovered, quite by accident, in the course of 

 his researches. He found that certain artificially-produced 

 lesions of the nervous system, so small even as a section of 

 the sciatic nerve, left, after healing, an increasing excit 

 ability which ended in liability to epilepsy; and there 

 afterwards came out the unlooked-for result that the 

 offspring of guinea-pigs which had thus acquired an 

 epileptic habit such that a pinch on the neck would produce 

 a fit, inherited an epileptic habit of like kind. It has, 

 indeed, been since alleged that guinea pigs tend to epilepsy, 

 and that phenomena of the kind described, occur where 

 there have been no antecedents like those in Brown- 



