388 MR. G. E. H. BARRETT-HAMILTON OW [Apr. 3, 



with an apology for the work in which he is engaged. So 

 long as the field of enquiry be entomology, the attempt to describe 

 and classify local variations, and to gain some knowledge of the 

 guiding principles which underly them, is regarded with respect. 

 If, on the other hand, a zoologist attempts to institute a similar 

 inquiry respecting mammals, he is regarded with suspicion, or often 

 as a mere species-monger who wishes to burden the compilers of 

 local faunas with the names of a number of forms, the status and 

 relationships of which only a long study will help them to thoroughly 

 understand. Tet modern investigations have clearly shown the 

 existence of a rich crop of local variations amongst the Mammalia, 

 not less worthy of study than those found amongst the Lepi- 

 dopteraor Mollusca, and which I hold it to be clearly the business 

 of systematic zoology not only to describe and to arrange, but to 

 name. 



In treating a species well known and long recognized, such as 

 Alussylvaticiis, 1 prefer to regard as subspecies all forms which can 

 be identified as in any way phases or representative modifications 

 of the original type as known to Linnaeus. The method, so much 

 in favour in America, whereby all forms which intergrade are looked 

 upon as subspecies, and all those which do not are regarded as 

 species, has much to recommend it; but the simp'e ascertain- 

 ment of the fact that intergradation does, or does not, occur alone 

 implies a greater knowledge and an ampler series of specimens than 

 we, in the Old "World, possess of many of the very commonest 

 mammals. Further, by its unavoidable multiplication of species 

 it obscures the relationship of kindred species and genera, and 

 necessitates the formation of new genera or subgenera to include 

 the various groups of new species and subspecies. Under this 

 system many, if not all, of our time-honoured Old World species 

 would be raised to the rank of full genera — a contingency which 

 may be eventually necessary, but which it seems desirable to 

 postpone to as late a date as possible. 



On the other hand, the system used in this paper has the 

 advantage of roughly indicating the relationship of the forms 

 dealt with. We do not, however, thereby escape from the 

 difficulty that these forms are of widely different degrees of 

 distinctness. For instance, whereas some of our western subspecies 

 approach each other closely, even in their extreme phases, and will 

 probably be found to intergrade freely, there are others, such as 

 Mus syhaticus prineeps or M. s. draco, which, even if they be 

 proved to intergrade, are in their extreme phases highly distinct and 

 at once recognizable. Some forms there are, however, which, having 

 been lon°- separated from the parent form, have become so differ- 

 entiated that the most stubborn disregarder of local variations 

 could not consider them to be identical with M. s. typicus. Such 

 is M. arcjenteus of Japan. To it accordingly, lest roy judgment 

 should be found erring in allying it too closely with M. sylvaticus, 

 I here accord full specific rank. 



A further advantage may be claimed for the method which is 



