that a Curculio bred in a Butternut would be just as likeh' as not to 

 lay its eggs in a Plum, and the reverse ; thus showing that here no dis- 

 tinct "Phytophagic species" has yet been formed. This was the opin- 

 ion of Dr. Fitch; for he says that- ''the specimens found on Butter- 

 nut trees are always larger in size than those found on cultivated 

 fruit-trees, indicating that they have been better fed during the larva 

 or growing period of their lives." (Address on Curculio, 1860, p. 

 17.) But there is a remarkable fact, which proves satisfactorily to my 

 mind that this cannot be so, and that the two races are perfectly dis- 

 tinct and do not interbreed, each confining itself strictly to its peculiar 

 food-plants. The fact is simply this : — I have beaten hundreds and 

 hundreds of (Jurculios of the small-sized type off fruiting wild Plum- 

 trees, but I never yet beat a single specimen of the large-sized type, 

 which inhabits Butternuts and Walnuts, off a Plum-tree of any spe- 

 cies or in any state. Of course, if that large-sized type had acquired 

 no hereditary indisposition or incapacity to breed in Plums, it would 

 be just as likely to occur on the Plum as on the Butternut or Walnut 

 But if, as the facts indicate, it really has acquired such a hereditary 

 indisposition or incapacity, and if it interbreeds only with its own 

 race, then — according to what I consider to be the essence of the term 

 "species" — it is a distinct species. You may, if you please, for the 

 sake of precision, give it a distinctive appellation, and call it, for ex- 

 ample, a "Phytophagic species; but still it is, in my acceptation of 

 the term, a true species. 



In the recent much enlarged and improved edition of the "Origin 

 of Species," Mr. Darwin has quoted with general approbation my 

 views upon this very interesting subject, but has incidentally re- 

 marked that I am "forced to assume that those forms which have lost 

 the capacity for intercrossing should be called species." (Fourth 

 English edition, pp. 55—6 .) This, I think, can scarcely be called an 

 assumption. It is a definition. Naturalists have been puzzled for 

 ages to designate satisfactorily what they mean by the term "species," 

 and all kinds of loose and shadowy and intangible explanations of the 

 term have been given; the latest discovery being that of an American 

 refuter of Darwinism, flourishing in the great city of New York, who 

 defines a "species" as a "specific form;" which is much like explain- 

 ing the term "yellow" by saying that it means "that which possesses 

 yellowness." Darwin himself maintains that species are not essen- 

 tially different from mere varieties. In their origin, I allow that they 

 are the same ; for I believe with Darwin that every species originated 

 from a variety of some pre-existing species. And I further allow 

 that there is a transition period, during which it is impossible to say 



