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 lateral lobes. Aud it is probable that we and others 

 have too readily succumbed to this temptation. 



It is in connection with this point that the term tegmen 

 becomes very usetul, for we can homologise the combina- 

 tion more certainly than we can the lateral lobes alone. 



The difference 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, etc. 



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 iStaphylinidae the part of the tube wall that is in so 

 many families chitinised to form the basal-piece, remains 

 membranous, and in other families ol 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 



