xv] ee) 
emerged. It implied a recognition of the fact that hard-and- 
fast lines were not easily found in nature. Here and there 
an isolated assemblage of individuals could be named, round 
which it would be possible to draw a definite line; but in 
many cases the delimitation of frontier must be arbitrary. 
The President had brought forward a striking instance in the 
case of Amauris niavius and A. dominicanus, which had been 
shown by Mr. Neave to be connected in the Uganda district 
by a complete series of intermediate forms. Still more strik- 
ing perhaps was the case of Jylothris chloris and M. agathina, 
which had always been considered as completely distinct as 
any two species in the genus, but which intergraded with one 
another in the same district of Uganda, In the genus Colias 
again, the speaker, after a careful study of Mr. Elwes’ well- 
known papers, found himself in complete agreement with the 
opinions there expressed as to the impossibility of separating 
various forms that had received distinct specific names. 
“Typical” forms, for instance, of C. paleno and C. chrysotheme 
in the Old World, and of C. philodice and C. ewrytheme in the 
New, were sufficiently dissimilar ; yet in certain parts of their 
area of distribution, these forms seemed to be inextricably 
interconnected. 
It appeared to be now admitted by many naturalists that 
the question, ‘‘ What is a species?” resolved itself into a 
matter of general convenience. What then, from this point 
of view, were the best criteria of specific distinctness? The 
President in his recent Address had suggested more than one 
such test. Of these the most crucial was probably epigony. 
It met such cases as those of seasonal dimorphism, where the 
syngamic test was inapplicable ; moreover it had the advant- 
age of getting rid altogether of the arbitrary element. 
Evidence as to syngamy was extremely valuable, and in most 
cases was more easily obtained; but it could hardly be said 
that syngamy used as a test of specific distinction was able 
to dispense with the personal equation, Syngamy was con- 
trolled by sexual preference; of this many degrees were 
known to exist. On the one hand there was perfectly free 
interbreeding, on the other the “rare and occasional inter- 
breeding” which, as Prof. Poulton said, “is not syngamy.” 
