414 PROCEEDINGS OF THE AMERICAN ACADEMY 



instincts were transmitted from the parents to their offspring. That 

 such acquirements, once inherited, would be likely to continue herit- 

 able, was argued to be the natural consequence of the general law 

 of inheritance, the most fundamental law in physiology ; that it is 

 actually so, Professor Gray insisted was well known to every breeder 

 of domestic animals. 



6. For decisive instances of the perpetuity by descent or fixity, 

 under inter-breeding, of altered structure, Professor Gray adduced 

 Manx cats and Dorking fowls ; and he alluded to well-known cases 

 of six-digited people, and the like, transmitting the peculiarity to 

 more than half of their children, and even gi-andchildren ; showing 

 that the salient peculiarity tended to be more transmissible than the 

 normal state at the outset ; so that, by breeding in and in, it was 

 likely that hexadactyles could soon be made to come as true to the 

 breed as Dorkings. 



7. As to the charge that the theory in question denies permanence 

 of type. Professor Gray remarked that, on the contrary, the theory not 

 only admitted persistence of type, as the term is understood by all 

 naturalists, but was actually built upon this admitted fact as one of its 

 main foundations ; that, indeed, one of the prominent advantages of 

 this veiy theory was, that it accounted for this long persistence of 

 type, which upon every other theory remained scientifically unac- 

 counted for. 



8. Finally, as to the charge that the hypothesis in question repudi- 

 ated design or purpose in nature and the whole doctrine of final causes, 

 Professor Gray urged : — 1. That to maintain that a theory of the deri- 

 vation of one species or sort of animal from another through secondary 

 causes and natural agencies negatived design, seemed to concede that 

 whatever in nature is accomplished thx'ough secondary causes is so 

 much removed from the sphere of design, or that only that which is 

 supernatural can be regarded or shown to be designed; — which no 

 theist can admit. 2. That the establishment of this particular theory 

 by scientific evidence would leave the doctrines of final cause, utility, 

 special design, or whatever other teleological view, just where they 

 were before its promulgation, in all fundamental respects ; that no new 

 kind of difficulty comes in with this theory, i. e. none with which the 

 philosophical naturalist is not already familiar. It is merely the old 

 problem as to how persistence of type and morphological conformity 



