218 Dr. David Sharp's Studies in Rhynchophora. 



The Sac. 

 The more intimate part of the copulatory mechanism is the 

 sac (called by some " praepntial sac," though the name is 

 a misnomer). This structure is predominately membranous 

 though it has various chitinous bodies in its walls. This 

 is the structure that enters the genital tube of the female, 

 one of the functions of the median lobe being to bring this 

 male structure into such a position that it can enter the 

 female parts notwithstanding its membranous texture. It 

 is protean in form, and exhibits the most wonderful diver- 

 sities of shape. A comparatively simple form is shown in 

 tig. I, a more voluminous and complex one in figs. 7 and 8. 

 In repose the sac is packed away inside the median lobe, 

 but most frequently the apex of the sac projects more or 

 less from the base of the median lobe, where it can be seen 

 with the duct entering it. The sac has a variety of struc- 

 tures in addition to its marvellous development of lobes; 

 these structures form the armature of spines and thorns, 

 as well as of minute papillae, etc. In addition to this 

 armature, there is an adjunct of the duct of an important 

 nature, placed in the wall of the sac where the duct enters. 

 In fact, this structure is the completion of the copulatory 

 mechanism. The duct enters it, and when the sac is 

 everted the apparatus is carried with it and becomes the 

 apical part of the sac ; the functional orifice is seated on 

 this little mechanism, and it is at this spot that the sperm 

 leaves the male part of the genital conduit and becomes 

 the appurtenance of the female. I call this the transfer 

 apparatus. It differs greatly in various Rhynchophora. 

 Our tig. 5 shows it in Polycleis plumbeus (a South African 

 Otiorrhvnchid), and fig. 6 exhibits it more highly magnified. 

 It is seen to consist of a median structure, into the base of 

 which the duct enters, terminating at its apex; the frame 

 part is subsidiary. A structure more or less like the 

 median portion of the apparatus (fig. 6) is very common, 

 and the form may be considered as a vase-like flagellum ; 

 sometimes by great elongation it becomes a slender or 

 whip-like flagellum, which may be several times as long as 

 the whole insect: but usually the flagellum is shorter than 

 this. I have examined this structure in a series of species 

 of the ^enus Holonychus, where it varies very greatly in 

 development, being in some larger than the flagellum of 

 Polycleis (fig. <»), while in other species it is minute and 

 (lilliciilt to detect. 



