606 Mr. D. Sharp and Mr. F. Muir on the Comparative 
their ontogeny. It will be noticed that they are paired, or 
longitudinal, in arrangement, whereas the other structures 
of the phallic part of the tube are single and transversely 
separated. This paired condition of the lateral lobes 
tempts one strongly to identify any paired processes on 
the phallic division of the tube (even when median) as 
being Jateral lobes. And it is probable that we and others 
have too readily succumbed to this temptation. 
It is in connection with this point that the term tesmen 
becomes very useful, for we can homologise the combina- 
tion more certainly than we can the lateral lobes alone. 
The ditference in position of the lateral lobes may be 
accompanied by their partial (or complete ?) consolidation. 
If the chitinisation of the basal parts of the lobes extend 
towards the longitudinal middle line of the tube at the 
expense of the membranous creases that exist, the two 
lateral lobes can become joined, and it is possible that the 
conjunction may go so far as to obliterate their primitive 
duality. This consolidation can occur either dorsally or 
ventrally, and we must look on a distinction so established 
(as has been pointed out by Verhoeff) as of great import- 
ance. It creates a difficulty in adjusting the position of 
various forms of “ Heteromera,” Cioidae, ete. 
Extension transversely of conjoined lateral lobes might 
lead to the formation of a tubular chitinous sheath such as 
we find in Trogositidae, Cleridae, Byturidae. Or such a 
sheath might be formed by unconjoined lobes extending 
both above and below, and if a sheath be formed, by abbre- 
viation it may become a “ring.” Or a ring may be formed 
by extension of the angles, or margins of the basal-piece. 
We can only briefly indicate some of the numerous modifi- 
cations that are possible of these phallic sclerites. 
In Staphylinidae the part of the tube wall that is in so 
many families chitinised to form the basal-piece, remains 
membranous, and in other families of the Staphylinoidea 
the basal-piece is small. In Tenebrionoidea the basal- 
piece is long, and usually forms the chief part of the 
aedeagus. 
Some morphologists have supposed (as we have already 
said) that the lateral lobes are modified abdominal append- 
ages; on the other hand it may be suggested that some 
Coleoptera have never possessed lateral lobes. This point 
is briefly discussed in the section of phylogeny. 
The internal sac varies in size, shape and armature in 
