1900. ] GROTE—THE DESCENT OF THE PIERIDS. BD) 
the kind in the Pierids. In the Parnassiide I have recorded an 
individual variation in the position of R2 and J/1 on the fore 
wings of Zerynthia. ‘The fact that these variations take the normal 
direction, seems to denote, that they are shown by anticipation 
(specialization) by a part of the mass ofindividuals before becoming 
fixed for the species asa whole. I have found no sexual characters 
in the neuration; these appear to be limited to the outline of the 
wings. Inthe male, ¢. g., Zachyris, the primaries are in special 
cases narrowed and more pointed at the tips; in Drsmorphia there 
is added to this narrowness in the primaries a compensatory greater 
breadth in the secondary wings. The female wing has been pre- 
ferred for study, since this sex seems the more conservative. I 
have, however, found no positive proof of this in the neuration, so 
far as the limited number of specimens studied will allow me to see. 
The neuration affords no assistance to the theory that the color and 
pattern of the female is influenced by atavism. In fact, I have not 
succeeded in showing that the color and veining move together at all 
closely, and have accordingly omitted almost everything not related 
to structure and shape of the wings. As with the Papilionides, how- 
ever, a white color, while persistent throughout a line, seems to 
be at least a secondary, not a primary color. The male, e. g., 
Perrhybris, Prioneris, Phrissura, Huphina, is apt to whiten, to 
become paler. 
But in Zxantia melite and in Colias rhamni the male is of a much 
deeper color, more yellow than the female, while the most special- 
ized and the most generalized forms alike show pale colors in the 
Pieridide. In size the butterflies seem to tend to becoming 
smaller, as seen in such specialized forms as Phu/ia and Wathalts. 
The total impression we derive of the neuration is one of con- 
tinuity. The forms lead from one to another with unequal gaps 
between the genera, hence the generic characters are unequal also. 
The changes in the position of the veins are no doubt mechanically 
caused by the strain of the organism against its media. The dis- 
parities are accentuated for the moment, related to those interfer- 
ences in the world process which are the ultimate cause of all 
diversity in nature. 
GENEALOGICAL TREES AND TABLES. 
In proportion as an intelligible system underlies the drawing up 
of genealogical trees and tables of genera are they of use and 
