70 Dr. F. A. Dixey on the Relation of 



here, we cannot, I think, feel any doubt that it is suffi- 

 cient to demonstrate the possibiUty of the formation of a 

 practically perfect mimetic pattern from the ordinary 

 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 eflPected 

 jyer saltma. 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. Sexual 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, 

 us 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. 



