288 Dr. Frederick A. Dixey on the 
of the cell, of which our native species of Colias and 
Gonepteryx present good instances, are relics of a more 
elaborate system of marking seen in a high condition of 
development in various exotic genera. This system 
consists essentially of a series of red and yellow markings 
occupying more or less completely the pale spaces in- 
cluded between the radially disposed dark lines that 
coincide with the nervures on the one hand, and the 
concentrically arranged dark spots or bars of the marginal 
and submarginal series on the other. That this system 
of markings is a very primitive one is rendered probable 
by the fact (1) that it is represented by vestiges in so 
many genera of both hemispheres; and (2) that it occurs 
in a well-developed condition in genera so widely 
separated in a geographical sense as the South American 
Leodonta and Catasticta, and the Australian and Indian 
Delias and Prioneris. Asa general rule, the spaces at 
the base of the wing tend to be occupied with red, and 
those on the dise and at the periphery with yellow; but 
in some cases, as has been seen, the red may encroach 
upon the submarginal yellow (as in Delias ceneus, 
D. eucharis, D. argenthona, etc.), or may be prolonged 
from the base in various directions across the wing 
(Hesperocharis hirlanda, M. lypera, M. pyrrha, and other 
American species of Mylothris). In the first-named 
genera, which exhibit the system in its full state of 
development, the distinction between the red and yellow 
markings is a perfectly easy one; but in such genera as 
Pieris, Leptophobia, Hesperocharis, Belenois, Ganoris, 
Synchloe, and Colias, whose markings are no doubt 
ultimately derived from the Catasticta and Delias pattern, 
it is not always easy to say to which part of the original 
system the relics that are present belong. On an in- 
spection of all the forms, it would, however, seem to be 
the case that those members of the yellow part of the 
system most often persist which are capable of being 
reinforced, as it were, by a neighbouring red patch 
towards the base of the wing. For instance, the most 
persistent marking of all is, as we have seen, the yellow 
precostal streak. ‘This is in most species of Leodonta 
and Catasticta closely bordered on by a bright red spot 
in the inner division of the precostal space ; and on tracing 
the condition of that space from these more ancestral 
genera downwards, through Pieris, Leptophobia, and 
