Anatomy of the Male Genital Tube in Coleoptera. 635 
have not found between Rhynchophora and Phytophaga 
any distinction that is valid throughout the two divisions, 
though it is not improbable that an extended study would 
reveal some important difference. At present the Phyto- 
phagoidea is by far the largest of the eight series. 
The question as to the distinctness of the series depends 
largely on the view that is taken as regards “lateral lobes” 
in Coleoptera. To explain the view we are inclined to 
take, a digression of some length is necessary. 
It has been suggested that lateral lobes may be modified 
appendages of the body. We have not found anything to 
support this view. Indeed if it were so they were doubt- 
less modified in the precoleopterous stage of evolution 
and the point would therefore only indirectly concern us. 
But we incline to another view on this highly speculative 
point. We suggest that Coleoptera are descended from 
ancestors in which the efferent ducts from the sexual 
glands, either as a pair or singly, opened on a membrane 
connecting the 9th and 10th ventral plates of the 
abdomen, while the orifice of the alimentary canal was 
placed immediately above the 10th sternite, which thus 
separated the two great exits. By slight elongation of the 
membrane of orifice of the efferent ducts, they were in 
repose withdrawn within the body cavity; and asomewhat 
analogous phenomenon occurring with regard to the 
rectum, the genital tube and the apex of the rectum 
became, in the imago, placed inside the body cavity. The 
10th sternite (between the two parts) shared their invagin- 
ation so that the external body wall was terminated 
behind by the apposition of the hind margins of the 9th 
abdominal sternite with the 10th, or some other, tergite. 
This apposition, with of course considerable and in some 
cases very great modifications, has attaied so great 
perfection that sometimes it is very difficult to see 
any opening at the posterior extremity of the body. 
According to this view the genital tube is merely an 
elongation of a connecting membrane between two ventral 
plates ; the modified 10th sternite either entering into 
the composition of the tube or not, as the case may be. 
It may be well here to remark that for the purpose we 
have now in view, we are mentioning only the simplest 
aspect of the matter. For our purposes it does not signify 
how many abdominal segments there were originally, or 
whether more.than one were indrawn either subsequently 
