( 447 ) 



pecnliarity not met with, or rarely met witli, iu otiier districts ; wliether all the 

 localised si)ecimens are different from the rest of the species ; whether a localised 

 variety is or is not connected with the other varieties by intergraduate specimens,— 

 in every case the presence of a localised pecnliarity indicates that the iudividnals 

 inhabiting the respective locality are on the way to develop divergently in con- 

 seqnence of some biological peculiarity of the locality. All these degrees of 

 divergency are distingnishcd from that higher degree which we have taken as the 

 criterion of specific distinctness by not conforming to the physiological part of 

 onr definition of species. By experiments it has been proved * that geographical 

 forms lose their distinguishing characters and fuse together with other forms of 

 the same species. Therefore, if all the coexistent specimens of a species were at 

 our disposal, the definition of the term " subspecies " wonhl l)e as follows : — 



A subspecies is a localised group of individuals of a species the mean of the 

 characters of which is different from the mean of the 'characters of all the other 

 localised groups, and ivhich ivill, under favourable circumstances, fuse together tcifh 

 other groups. 



However, the material contained in collections is, compared with the actual 

 number of specimens existing of each variety, extremely meagre, though nowadays 

 systematists comprehend more and more that a few specimens of each species 

 are insufficient for a serious study, and hence try to briug together long series from 

 every locality. The conclusions, in respect to variation, which we draw from the 

 inadequate material we have to work with, must necessarily often be erroneous. If, 

 for example, our series shows a variation of a character (expressed in numbers) 

 between twenty and fifty) there may, in fact, exist individuals which stand outside 

 these limits. Rare varietal specimens, which hitherto have been found only in a 

 certain locality, may very well occur elsewhere ; a certain variety may appear to us 

 more common in one locality than in another, and hence the mean of the characters 

 in the first locality to be different from the mean in other localities, because a 

 collector paid more attention to varietal specimens in the first locality. This imjier- 

 fectness of our knowledge we have to take into account, and we must, therefore, 

 restrict the ap])lication of the term " subspecies " in order to avoid deception as far 

 as possible. 



The above definition has not had regard to the degree of divergency attained by 

 the localised form. Now, we ask, which then is the lower limit of application of the 

 term " subspecies " ? The diversity which tlie sexes exhibit in respect to localised 

 variation gives us the answer. We know a good many cases iu whicli the w^fe.s 

 are in various districts not distinguishable, while the females are very different, 

 and cases in which the variation takes jilace in the male sex and not in the 

 fenuile sex. For illustration we refer to the following insects : Papilio semperi, from 

 the Philippine Islands, varies in the female sex according to locality, while the 

 males from the various islands, in spite of individual variability, are not distinguish- 

 able ; Papilio oenomaus, from Timor and Wetter, is on tliese two islands the same 

 in the male sex, while the females are conspicuously different ; and so it is with 

 Papilio phestus, from New Britain, New Ireland, and the Solomon Islands. If we 

 api)ly in these cases, the importance of which we shall soon endeavour to show, the term 

 " subspecies," we have a rule which can guide us in all otlier cases— namely, as the 

 numbers of specimens of eacli sex can be taken as being (roughly) equal, we shall 

 have to use the term " subspecies " when a localised variation is such that about half 

 * Kerncr Giitc und Schlechtr ArU-n ; Weismanii Sliidiin zur m-siindenztluorie, 



