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 that 
the sac is evaginated ; in fact, the chitinisations on its base 
prevent such a thing. In this case muscular contraction 
round the 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withdrawn from the uterus of the female while the sac is 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, 
