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Show 8 MR. U.J. ELWES ON THE GENUS PARNASS1US. [jan. 19, ample, in another 100 pairs may be insufficient to illustrate all the points in the history of a species. With respect to the development and function of the pouch in this genus, which appears to m e interesting not only to lepidopterists but to all students of Biology, I must here acknowledge the assistance I have received from Mr. A. Thomson, of the Society's Gardens-who undertook and carried out in a most painstaking manner the observations on living insects, of which an account is given below- and especially to Mr. Salvin and to Prof. Howes, of the Biological Laboratory, South Kensington, who undertook the difficult and delicate task of dissecting and examining the specimens preserved by Mr. Thomson at the Gardens. And though much remains to be done before we can say that we fully understand this intricate question, yet a distinct advance has been made on our previous knowledge, and certain facts which were previously doubtful or obscure have been proved. The first writer who seems to have paid much attention to this organ was Von Siebold, who published in the 'Zeitung fiir wissenschaftliche Zoologie,' 1850, iii.pp. 54-61, and reprinted in the 'Stettiner entomologische Zeitung' 1851, pp. 176-185, a long and most valuable paper on the subject, aprecis of which, from an English translation kindly lent me by Mr. Gosse, I am here able to give:- The first part is historical, and shows that though Linnseus, Latreille, and Schiiffer had mentioned the existence of the pouch and described its form more or less incompletely in P. apollo and P. mne-mosyne, no one had carried these observations any further. Ochsen-heimen accepts its existence in the female as a generic character of Doritis, and Boisduval separates Doritis apollinus from Parnassius because it has no pouch. Siebold doubted whether the organ really formed part of the body, as he found that he could easily separate it in P. mnemosyne, and, with more difficulty, in P. apollo, as in this species it is glued more strongly by its base to the underside of the abdomen. He then suggests that it originates during copulation, in these words : - " Probably from the male or female individual, at the anal region there is secreted a clammy coagulable fluid, poured forth during the close association of the genital organ of the male with that of the female, which, by coagulating and hardening, produces a firm and long-enduiing union of both sexes. Alter the end of the copulative act, and after the complete severance of the sexes, there remains this coagulated substance as a sort of cast or impress of the hinder parts of the male in the vicinity of the sexual orifice of the female, a witness of the accomplished coitus." He then states that virgin females fresh from the pupa have no pouch, and says that Hbger was mistaken when he suggested that the pouch was afterwards protruded from the body for the purpose of oviposition. He then goes on to state that a chemical examination of the substance of the pouch by Dr. Baumert showed that it had no affinity with the chitinous substance of the body of the insect, which was insoluble when treated with caustic alkali; whereas the pouch of both P. apollo |