( xlix ) 



" It might seem that by the aid of organs so uniformly present, 

 so easily examined, and so varied in different species while 

 constant in the same, great facilities must be afforded for 

 the determination of specific identity and limitation. Yet, in 

 practice, I fear this cannot be carried out, without severing 

 species which otherwise seem most closely allied, and linking 

 others which have little else in common. Look, for instance, 

 at the three African species, Papilio Bromius, P. Nireus, and 

 P. Phorcas ; how consimilar are these in their forms, colours, 

 and markings ! yet how diverse in their whole prehensile 

 apparatus ! The shape of the valve, its fringing ; the shape of 

 the harpe, its armature ; the uncus ; the teeth of the scaphium ; 

 and finally the penis ; — all these differ signally in one from their 

 conditions in the others. The like terms might be employed 

 concerning P. Demoleus and P. Erithonius." 



" If it be asked, What is the definite purpose, in the economy 

 of the creature, of this extreme variation ? I am obliged to 

 answer, I do not know. That, viewed in the large, the object 

 of all these organs that crowd around the termination of the 

 male abdomen is the firm grasp and sustained retention of 

 the female abdomen, in the delicate and most essentially im- 

 portant function of reproduction, is sufficiently evident. But 

 why the diversity of detail ? Why would not one good and 

 adequate form suffice, again, and again, and again, subject to no 

 more variation than are the antennae, for example, or the tarsi ? 

 It naturally occurred to me, very early in these researches, that 

 every peculiarity in the prehensile organs of the male would 

 have a corresponding peculiarity in that part of the female body 

 which they were formed to grasp : and I eagerly turned to the 

 examination of the female abdomen. But the repeated search 

 left, and still leaves, my question — cui bono? — without an 

 answer." 



The question may be asked, says Mr. Gosse, " What homology 

 (or analogy ?) exists between the organs herein described by me 

 and those of the Trichoptera described by Mr. M'Lachlan. I have 

 examined every figure in his great work, and confess that I know 

 not how to institute any satisfactory comparison with those parts 

 in Papilio. It is just possible that the ' dorsal process,' in such 

 forms as Pilujacophila, may be equivalent to my ' uncus'; but of 

 ' scaphium ' I see not a trace. Possibly, too, the ' inferior 



