70 Dr. F. A. Dixey on the Relation of 
here, we cannot, I think, feel any doubt that it is suff- 
cient to demonstrate the possibility of the formation of a 
practically perfect mimetic pattern from the crdinary 
form of a quite distinct type, without any violent or 
abrupt changes of design. It does not, indeed, lend any 
support to the view that mimicry can only originate 
between forms that already possess considerable and 
obvious resemblance to one another, nor does it coun- 
tenance the opinion that mimetic changes are effected — 
per saltum. What the series of forms here figured does 
show is that, granted a beginning however small, such as 
the basal red touches in the normal Pierines, an elaborate 
and practically perfect mimetic pattern may be evolved 
therefrom by simple and easy stages. 
II. Sexuat DimorpHism In Mimetic Forms. 
There remains, in regard to the foregoing series, a 
question of great interest ; namely, what is the meaning 
of the diversity between the sexes in these more or less 
completely mimetic forms? Why should the one sex 
have advanced so much further along the mimetic path 
than the other? It is no doubt the case that the females 
stand in greater need of protection than the males, but 
to say this still leaves several questions unanswered. 
Are we right in regarding the male patterns as perpetu- 
ating stages through which the other sex has also 
passed in order to reach its present state of mimetic 
completeness, or are we to suppose that the selection by 
enemies has affected only the female sex, and that the 
patterns seen on the males are merely an incidental result 
of heredity, being, in fact, a secondary version of the 
female pattern transmitted in a weaker form? In either 
case, what has checked the further development of 
mimicry in the male? Is this imperfect development 
simply a passive result of the absence of necessity for 
change, or is there some active force at work preventing a 
further modification ? It is well known that an explana- 
tion of a somewhat similar case has been sought in the 
p:inciple of sexual selection ; the females, it was suggested, 
as the more conservative sex, preferring in their mates the 
ancestral type of coloration of the group.* Mr. Wallace, 
* Belt, “ Naturalist in Nicaragua,” Ed. 1888, p. 385. 
