Tin-: JU'TTKUFl.V : INTKKNAI. OIKJANS. 47 



niiiy bo mentioned here the ghinds and .similar strnetnres -whieli open ex- 

 ternally in butterflies. Allusion has already been made to those which 

 find their outlet through the scales, and probably there arc others which 

 find a passage through hairs in various parts of the body — such as in the 

 erect row found on the upper surface of the hind wings of the male Argyn- 

 nis, as in some instances has been proved to l)e the case in moths. But in 

 some of the higher butterflies, as in our own Anosia, we have a protrusile 

 pencil of long hairs (61:19,59), which appear to be cylindrical tubes, lying 

 in sheaths on each side of the eighth abdominal segment of the male ; and 

 in an almost precisely equivalent position on the same segment of the 

 female of allied butterflies (Colaenis, Ileliconius, Eueides, Dione, Acraeaj, 

 Fritz Miiller has shown the existence of a pair of protrusile vescicular 

 organs clothed with scales, which are distinctly odoriferous and undoubt- 

 edly connected with sexual functions. 



The internal organs (PI. 62: tigs. 2 4). 



Although the internal organs of butterflies are brought to their full per- 

 fection at the close of the pupal condition, and have therefore been already 

 outlined to a certain extent, yet as the account has been coupled with 

 statements of the changes undergone in the larval organization to effect the 

 required result, it may be worth Avhile to give here a succinct account of the 

 completed structures, following the same order as heretofore. The published 

 materials for such a survey, it may be remarked, are exceedingly scanty, 

 and my own dissections have been largely confined to the earlier stages. 

 The only general sketch yet published is that by the indefatigable Leon 

 Dufour (Comptes rendus, 1852), l)at an excellent outline is furnished in 

 his complete anatomy of Anosia plexippus (Anniv. mem. Bost. soc. nat. 

 hist.) by my gifted friend Edward Burgess, whose loss to entomotomy is 

 <^)idy partially conqjcnsated by the gain to scientific naval architecture. 



Muscular system. The great mass of the muscular tissue is now 

 developed in the thorax and principally to direct the action of the wings ; 

 these muscles form two principal sets : one longitudinal, by far the most 

 numerous, which serve to depress the wings by shortening the thorax ; the 

 other a transversely oblique set, attached below to the floor of the thorax, 

 and above to the bases of the complicated structure of the inner frame work 

 of the wing, acting thus at great disadvantage as a lever ; besides these 

 a third accessory set running from the scutellum between the other two 

 sets to the front base of the wings, serves to draw them forward. All 

 other muscles of the body serving to move external ap})endages are 

 attached to the walls of the body in the immediate vicinity of the organ to 

 be moved or to special ridges or inner outgrowths of the walls ; while the 

 internal organs may have their independent muscles as in the early stages ; 

 some of these will be mentioned in their place. 



