( 502 ) 



specifically distinct from its allies, and that it is circnmstantial evidence which has 

 to guide us, in the absence of experiments, iu onr judgment. Now, what is the 

 evidence we derive from the examination of the organs of copulation ? 



We know the larval and imagiual state of a good many Papilios, and are able 

 to base on our knowledge of their organisation, quite apart from the characters of the 

 organs of copulation, a classification in which the most nearly allied species are, 

 with a certain degree of correctucss, grouped together. If we now compare of a 

 well-stndied group such forms about the specific distinctness of whicli we do not 

 entertain any doubt — if, for example, we examine the sexual armature of P. nicmnoit, 

 mayo, oenomans, polymnestor, lampsacus, /•umanzocius, etc., which in their general 

 organisation are all more or less closely allied to P. memnon, or take for examination 

 P. anfiplintes and undrocles, or P. aristolochiae and P. pobjdorus, or the various 

 yellow species of Troidcf- ( = Or/iit/iopti'/ri) — the first thing we notice is that the 

 imagines of each species exhibit, besides the distinguishing characters in colour and 

 structure externally visible, also characters iu the genital armature peculiar to the 

 resj)ective species. As we have not found amongst all those sj)ecies the specific 

 ilistiuctness of which we could de<Iuce from characters other than such of the organs 

 of copulation a single exception to that rule, we hope we are justified in generalis- 

 ing the statement that every species of Papilio is different from every other 

 species in the sexual armature ; aud this generalisation we believe the more con- 

 fidently to be correct as also iu other groups of Lepidopti'ra sjiecifically distinct 

 forms are characterised by some peculiarity in the copulatory organs, although the 

 difference between allied species is sometimes — for example, among Aganaidae — 

 very slight. If the generalisation is correct— i.e. if every form that is, according to 

 onr definition of the term " species," specifically distinct, whicli, we repeat, can only 

 be prori'd by experiment, and we will assume the generalisation to be correct — then 

 it follows necessarily that ft)rms which are identical in the genital armature are also 

 s]iecifically identical. If we apply this conclusion to the species of Papilio exter- 

 nally polymorphic, it is evident that the genital armature of male and female is an 

 excellent criterion of specific identity. The various varieties of the male, of 

 P. aegeas ormenus from New Guinea, of Troidcs priama.% poseidon from the same 

 country, of P. memnon, and so on, many of which have been described as distinct 

 species, are thus easily demonstrated to be specifically the same. Still more 

 important is the application to t\\e, female sex. The numerous species with poly- 

 morphic femalea which so often are quite unlike each other, as in the case of 

 P. memnon, P. aeyeus ormenus, P. poh/tes, and the African P. pkorcas and merope, 

 aud some American species — an examination of the genital apparatus of a number 

 of specimens wUl at once make it clear whether the forms in ipiestion belong 

 certainly to one species, or whether they eventually cau belong to more sjiecies. We 

 say intentionally " a unmber of specimens," for the examination of one example of 

 each form is (|uite inadecjuate, aud may lead to entirely erroneous conclusions. 

 F. 171 aud 17;i give au excellent illustration, the first being taken from a tailless 

 example oi P. memnon agenor from Sikkim, and the other from a tailed sjiecimen 

 from the same locality. Now, considering that f. 167 represents a species very 

 different from memnon, it would by no means be preposterous to conclude, if one had 

 to judge only from the three figures and the conspicuous external differences of the 

 specimens, that f. 171 and 173 represented likewise specifically diftereut Papilios. 

 It will generally -be quite sufficient to examine a number of individuals of one of the 

 forms, and til determine thus the probable limits of variation : the vaginal ap])aratns 



