( -Mn ) 



])relieiisile organs of the mali>. would liave a corresjioiidiug jiecnli.irity in that part 

 of the fumale body which they were foriued to grasp," but he failed to discover 

 " the corresponding pecnliarity in the femdle" as he labonred nnder the erroneous 

 assumption that "it is the cxfirior of the final segments of th.Q female abdomen 

 that are seized in coitu.'''' We have been able to show in the Ijody of this jiaper 

 that the male claspers seize in copulation the protruding vaginal bulb, taking hold 

 on chitinised folds and riilges, and not the terminal segments ; and we have further 

 been able to demonstrate the following two important points : — 



(1) We have a pair of Papilio niemnon united in coitu, from which we see 

 clearly that the harpe of the iiuilc fits exactly the lateral ridge of the vaginal bulb 

 of the J'emale, while the high and broad processes at the mouth of the vagina, 

 besides being a guide to the penis, take hold on the internal parts of the ninth 

 segment of the male. When uniting artificially males ami /ema/eti of other species, 

 we find that the organs of one sex fit those of the other of the same species, while 

 the copulatory organs of diflereut species, for instance of a male of F. marhaon and 

 z. female oi P. podalirius, or of memnon and helenus, (io not fit each other. We 

 are therefore justified in concluding that the organs of the sexes of the same species 

 are better adapted to each otlu^r than to the organs of other species. 



(2) The vaginal armature is in every species of Papilio examined difterent 

 from that of every other species examined. As our researches, only part of which 

 have been laid down in this pajier, relate to a great many species of various groups 

 oi Papilio &nd othar Lepidopteiv,v,'e can safely say that the females of every species 

 are, like the males, in the sexual armature distinguished from the females of every 

 other species. A comparison of the figures on PI. XIX. will show that the 

 divergency between the apparatus of representatives of diverse groups is in every 

 respect so great, that it is readily conceivable that a ?nale the aj)paratus of which 

 is adapted to such organs as represented by f. 181 cannot effectively copulate with 

 n female the organs of which are so ditt'erent as those represented by f. 163, 179, 

 or 182. 



The position of the vaginal orifice and the lateral fold of the vaginal bulb, 

 the number, length, and position of the ridges and processes at the orifice of the 

 vagina, and the develojjmeut of the eighth segment of the female, as well as the 

 special structure of the clasping organs of the male, are in diverse groups of Papilio 

 so widely different that there can be no doubt that the divergency in the organs of 

 copulation has rightly been interpreted by Siebold as a means of prevention of inter- 

 crossing. It is obvious that the more the organs of different species resemble each 

 other the less they will be able to prevent copulation. In closely allied species, 

 therefore, the effect of this mechanical barrier against intercrossing will generally 

 be less great than in the case of more direrse forms; but we must recall to mind 

 that even in the most closely related species, such as Papilio eachenor and depilis 

 (f. 51 and 65), the organs of copulation, though built up after the same plan, can 

 in the position and direction of the spines, hooks, and ridges of the harpe be so 

 different that the pi'ehensile organs of the 7nale come in contact during copulation 

 with quite different points of the vaginal region of the female, and that it is accord- 

 ingly also in such cases obvious that an intercrossing is not possible without violence. 

 In groups of Lepidoptera in which the genital armature is very simple the efiect 

 as a mechanical barrier must necessarily be very slight ; this seems to us to be one 

 reason why specimens of diverse si)ecies of Saturnidae, for instance, copulate much 

 easier than is the case with specifically iliffercnt individuals in other groups. 



