638 Mr. D. Sharp and Mr. F. Muir on the Comparative 
Returning then to the Elaterid he will notice that the 
change required to permit the tegmen in that form to 
ride over, or cloak, the median lobe consists in the first 
place of an elongation of the connecting membrane between 
them. If this take place and the liberated lateral lobes 
be approximated dorsally, we have in fact the essentials 
of the arrangement as we find it in Cucujidae. We might, 
then, conclude that it is permissible to. derive the Cucu- 
joidea from the Byrrhoidea. When, however, we turn to 
consider whether such a change has ever actually occurred, 
we must ask ourselves whether it is probable that an 
aedeagus that is functioning as an organ of one layer 
would change into a structure that functions as a two 
layer arrangement. We think the answer would be that 
in the early conditions of the genital tube such a change 
might occur, but that after the aedeagus had attained a 
considerable development nothing of the sort is at all 
probable. 
We now return to the consideration of the Phyto- 
phagoidea. Ifa well-developed Cerambycid aedeagus (say 
one of Clytini) be compared with Cucujus it will be noticed 
that in the position occupied by the “lateral lobes” (af 
really such) of the latter there is in the Clytus a divided, 
or rather cleft, process resembling the Cucuwjus lobes, and 
it would appear therefore that if the Cucujus possesses 
lateral lobes so also may the Clytus. 
A further examination of a variety of forms of the two 
series produces the gravest doubts. In the Cucujoidea 
the lateral lobes are either articulated at the apex of the 
tegmen, or if the articulation be absent, the single part 
has the appearance of being two parts combined (cf. 
Helota). But in Phytophagoidea (at any rate in Ceramby- 
cidae) there is never any articulation of the apical processes 
of the tegmen, and the comparison of a series of forms 
suggests that the bilobed state of the apex of the tegmen 
(or cap-piece) may be the result of progressive emargination 
of what was originally a single piece.* In that case the 
* In the Cerambycidae (especially marked in genus Phiissoma), 
there is a ridge on the underface of the divided cap-piece giving an 
illusory appearance of articulation of the two lobes. In the Curcu- 
lionidae the appearance is different: there are often two separated 
lobes (the ‘‘ papilla” of Hopkins in Pissodes), and in Ewpholus the 
lobes are widely separated (this point is not well shown in our 
fig. 222), while in some other Rhynchophora there is a single 
median prolongation of the cap-piece. None of these cases is similar 
