of the male genital tube in Coleoptera. 227 



where the surface of the body wall does not allow a large 

 enough surface for the attachment of muscles. In Rhab- 

 docnemis obscura (Boisd.) the spiculum arises from the side 

 of the pseudo-tegmen some distance from the opening of 

 the cloaca, and, as already stated, in Rhynchophorus there 

 is no spiculum. In Platypus also the spiculum is absent. 

 It is probable that the spicula in different groups are not 

 homologous. 



The theory of the origin of the genital tube by the 

 amalgamation of paired organs finds its chief support in 

 the analogy drawn from such forms as the Dermaptera. In 

 that order there is a Y-shaped organ consisting of a single 

 basal piece with a pair of parameres. In one group 

 (Protodermaptera) there are two penes, one arising from 

 each paramere ; in another group (Eudermaptera) there is 

 only a single median penis. This latter form is similar in 

 construction to the trilobe form of Coleoptera. I can find 

 no evidence to show that the single basal portion of the 

 organ is formed by the amalgamation of two parameres, 

 and it is quite possible, and even probable, that the para- 

 meres are secondary developments, the same as the tegminal 

 lobes in Coleoptera. The formation of the single median 

 penis of the Eudermaptera is not by the amalgamation of 

 the two, but by the suppression of one penis and the increased 

 growth of the other. Thus the analogy from Dermaptera 

 gives no support to the theory of the paired origin of the 

 tegmen, and refutes the theory of such an origin of the 

 median lobe. 



It may be thought (though there is no evidence to indi- 

 cate it, and it is very improbable) that Coleoptera had paired 

 genital openings, or that Protocoleoptera possessed them. 

 The time when the ancestors of the order could have been in 

 that condition is so remote that it can have no bearing upon 

 the question. It is probable that the immediate preceding 

 stage to the Coleoptera or Protocoleoptera was such as is 

 found to-day in Zoraptera Silvestri, where there is a single 

 duct opening in a median position, a portion of which is 

 most probably protruded during copulation. It is the 

 telescoping and chitinisation of this eversible portion of 

 the duct that has constituted the organ as we now know it. 



In the Anoplura and Mallophaga we have an arrangement 

 of parts in the male genitalia similar to those in the trilobe 

 forms of Coleoptera, with similar lines of development in 

 both groups. That these are cases of parallel development 



