MUSEUM GF COMPARATIVE ZOOLOGY. 2-17 



neet'ed, (han would be deemed necessary for specific separation ; and so 

 long as the extr raes only were known, no one could have regarded them 

 otherwise than as well-defined species. But the time has already come, 

 it seems to me, for a different and a more philosophic method, and that 

 to furl her increase synonymy by giving new names to slightly different 

 local forms of the same species is worse than useless. 



It is important, in this connection, to observe that the species occur- 

 ring at any point on the Atlantic coast, or on the Pacific coast, or in 

 the Mississippi valley, or on the Great Plains, in short, at any re- 

 stricted locality, have, as compared with each other, with scarcely an 

 exception, an unequivocal character ; they are based on differences that 

 place them beyond controversy. It is not so, however, when we com- 

 pare the species of distant localities with each other, whether the 

 localities differ in latitude or longitude. In such cases we constantly 

 meet with controverted species. At the South are species admitted 

 as doubtfully di.-tmct from others found farther north; at the West, 

 those holding the same relation to others of the East ; while at in- 

 termediate points either both the disputed forms occur with greater 

 or less frequency, or there is a gradual transition of the one into 

 the other, neither form being typically represented. This is evi- 

 dently what should be expected to occur, if what has been said above 

 in respect to climatic variation be correct, and is evident^ a suggestive 

 and important fact. Is the theory of hybridization, so often appealed to 

 in such cases, necessary to explain these facts ? and is it, in fact, true ? 

 By uniting the intergrading forms, the number of species occurrin"- at 

 any >ingle locality is not essentially reduced, but such a union would 

 considerably reduce the total number recognized, as well as the num- 

 ber usually assigned to the several continents, as at present not a few 

 fire repeatedly counted. 



The many facts bearing upon individual and geographical variation, 

 presented in the foregoing pages form but an imperfect exposition of 

 the subject. They are, nevertheless, eminently suggestive of interesting 

 results, and the conclusions above deduced I can but believe will be 

 only the more fully confirmed by further research. Additional details 

 are given in the general remarks embraced in Part IV, where various 

 fact- merely hinted at above are more fully presented, and an appli- 

 cation is made in many cases of the pinciples deducible from them. 



As previously stated, individual and geographical variations are in 



