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Show 1886.] MR. H. J. ELWES ON THE GENUS PARNASSIUS. 7 the exception of two or three species, so slight that it would be quite premature to write a monograph of the genus. But, partly-through the numerous scientific explorations which have been carried on in Russian Asia of late years, and partly owing to the high value placed on these Butterflies having encouraged the efforts of professional collectors in remote parts of Turkestan, so large a number of specimens have reached Europe during the last five or six years that a review of the genus is both possible and useful. The principal object, however, in m y work has been to investigate the functions and structure of the horny pouch-like appendage wdiich is found in the female sex of the genus, and which seems to have been almost entirely overlooked by most of those who have classified and described the species. I had not appreciated the immense importance of this structure, as a specific aud generic character, until I received two years ago, through the kindness of my friend M . Charles Oberthiir, of Rennes, a specimen of the magnificent Parnassius imperator from East Tibet; but when I saw how strongly it resembled P. charltonius of West Tibet in everything but the form of the pouch, whilst this organ was remarkably different, I saw what appeared to me a structural character of the highest value, and was led to an examination of the whole genus, which, on account of the extreme tendency to variation in size, and in the number and colour of the ocelli and markings- which had previously been considered as the principal characters by which to distinguish the species-was in a most unsatisfactory state of confusion. The result of m y examination is here given ; and I may say that, however faulty and incomplete it may be, I have taken every pains to bring it up to date, and have personally examined the principal collections, both public and private, in Germany, France, Russia, and England. I have thus been able to see, and to a certain extent compare, large numbers of almost all the known species, and though my conclusions may not be accepted by those whose interest and pleasure it is to multiply synonyms, and thus to increase the difficulty of the study of Lepidoptera, yet 1 believe that as far as it goes it is based upon facts alone. M y own collection, a part of which is now shown, contains about 400 specimens of the 23 species which I recognize in the genus, and includes both sexes of every described species except two. Though this number may seem large, yet I believe that it is not more than half of what would be required to illustrate perfectly such variable species as are most of the Parnassii, and though 1 have a long series of many, I have kept no specimens which are not necessary to illustrate some fact either of geographical distribution, of variation, or of range of altitude and season. And such I imagine should be the object of every scientific collector in any branch of natural history. W e too often see, in British collections at least, a fixed number of specimens exhibited in order to complete a row; but it is evident that whereas in some species of restricted habitat and little or no tendency to variation, two or three pairs may be |