54 GROTE—THE DESCENT OF THE PIERIDS. [Jan. 5, 
VALUE OF GENERIC CHARACTERS. 
This study of the wings of the Pierids will, I think, demonstrate 
that there exists no standard by which we can decide what consti- 
tutes or how much character should underlie the idea of a genus. 
The difference between the genus and species idea is quantitative 
merely. The conception of a genus as an independent entity, as in 
itself a thing closed and with real outlines and bounds, which it only 
requires a trained understanding to recognize, is seen to be illusory. 
The apparent limits of the genera are due, like those of the species, 
to gaps in the record. When these gaps are slight the lumpers 
ignore them, forgetting that the main business of entomology is to 
exhibit differences, not to lay stress on resemblances. The needless 
erection of genera should, indeed, be avoided, no less than the 
overlooking of distinctive characters. But what is here ‘‘ need- 
less ?’’ One can only illustrate what one subjectively considers 
needless by examples. The generic term Xanthidia seems to me 
quite unnecessary. On the other hand, I would retain the Antho- 
charid genera, although superficially much alike, because they empha- 
size certain stages in the specialization of the radius, which we are 
obliged to notice and discuss. Zefracharis, for instance, repre- 
sents a four-branched type in which #2 has not yet attained the 
Trifurcula position ; as such it is as much entitled to a generic 
name as another form not yet recognized as a member of a chain in 
which the links are so continuous. Everywhere, however, the 
links exist or have existed. It is not only that it is improbable that 
Nature has here progressed by jumps, but we cannot draw the line 
anywhere with exactness between such jumps as shall, and such as 
shall zof be entitled to generic recognition. It becomes thus a sub- 
jective question, to be settled by each observer, accordingly as he is 
soberly or extravagantly inclined in either direction, as to making 
many or making few genera. I myself tend in the direction of 
making many, for fear of passing over characters of structure and to 
avoid packing away distinct types of succession in onecategory. It 
becomes, finally, clearer, that many more kinds of butterflies have 
perished than are now to be seen; the tertiary and quaternary 
faunze seem specifically different. 
Certain of the characters of neuration here recognized as of 
generic value, so far as regards the movable veins or branchlets, are 
apt to appear as characters of variation within the limits of the same 
species of butterfly, although I have not noticed any variation of 
