Anatomy of the Male Genital Tube in Coleoptera. 611 



In certain forms the median lobe is specially contrived 

 to effect this blood pressure. In Xantholinus the median 

 lobe forms a chitinous egg-shaped chamber, having a 

 membranous band round the middle ; muscles pass from 

 the dorsal chitinous portion to the ventral chitinous portion. 

 The contraction of these muscles causes the chitinous 

 portions to approach one another, and thus exert pressure 

 on the fluid in the bulb which forces out the long internal 

 sac. In the case of Pinophilus where the sac is exceed- 

 ingly long, and lies coiled up, with a chitinous flagellum 

 running right through it like a spring, it is not likely tliat 

 the sac is evaginated ; in fact, the chitinisations on its base 

 prevent such a thing. In this case muscular contraction 

 round tiie coiled sac causes the distal end of the flagellum 

 to be thrust out through the median orifice, the chitinisa- 

 tions on the base of the sac acting as a guide ; upon the 

 relaxation of the muscles the flagellum acts as a spring, 

 the coils distend, and the distal end of the flagellum is 

 retracted. 



The action of the flagellum is obscure, but the fact that 

 it appears in such diverse families denotes its great func- 

 tional importance. It would be of great interest if some 

 one would take any form in which this structure is greatly 

 developed (e. g. Lucanidae, Brenthidae) and kill while in 

 copula and dissect the female, to see if any part of the 

 internal sac is evaginated, and to what part of the female 

 genital tube the flagellum penetrates.* 



In the Longicorns the capacious sac is very long, and it 

 seems improbable that it is entirely evaginated, but only 

 direct observation will decide this point. 



The various spines and hairs that are found on the sac 

 are generally pointed basally ; this prevents the sac being 

 withdrawn from the uterus of the female while the sac is 

 distended. The various diverticula found on the sac do 

 not appear to correspond to diverticula in the female, but 

 they take up constant positions, and may serve as pads to 



* Since writing the above one of the writers, F. Muir, has observed 

 the copulation of Cryptomorpha desjardinsi. This is a Cucujus-type 

 with a ring-shaped tegmen with a pair of lateral lobes, a long internal 

 sac with a very long and slender flagellum. In this species the 

 whole of the long internal sac is evaginated and enters the long 

 female tube, the flagellum proceeding still further into the female 

 genital tube. The spermatheca is small and attached to the uterus 

 by a long slender duct. Whether the flagellum actually traverses 

 this duct and penetrates the receptaculum he was not able to observe. 



