226 Mr. F. Muir's Notes on the Ontogeny and Morphology 



eighth spiracle is plainly discernible in both these genera. 

 In Hylesinus crenatus there is no chitinised eighth sternite, 

 and the spicnlnm is highly developed and serves in the place 

 of the sternite as part of the tube through which the 

 aedeagns plays. In some allied forms the eighth sternite 

 is represented in various states of dechitinisation (or degener- 

 ation). The anal opening in these forms is situated on the 

 membrane between the eighth tergite and the aedeagus 

 (on the dorso-basal portion of the connecting membrane). 



Conclusions. 



The evidence derived from observations on the develop- 

 ment of the male genital tube in Coleoptera indicates that 

 it is a tubular organ arising in a median position from the 

 connecting membrane between the ninth and tenth sternites. 

 There is no evidence whatever to indicate that it is composed 

 of amalgamated paired organs (called parameres by some 

 authors). The tegminal lobes, cap-piece and tegminal 

 strut are secondary outgrowths from the tegminal fold. 



The comparative study of the morphology does not indi- 

 cate that any abdominal segment or sternite is incorporated 

 into the tube. In certain forms we find that ten tergites 

 and ten sternites are actually present, or ten tergites and 

 nine sternites, and the aedeagus consists of complete tegmen 

 with tegminal lobes and basal piece and complete median 

 lobe ; in other forms some of the segments or parts of seg- 

 ments are dechitinised and withdrawn into the cloaca, but 

 the aedeagus in these forms only contains the same parts as 

 do those forms in which the segments are chitinised and there- 

 fore demonstrable. It is therefore illogical to consider the 

 missing segments as incorporated into the genital tube. 

 In fact the evidence points the other way, as in those forms 

 in which the abdominal segments are reduced there is 

 generally a great reduction in the tegmen. As the spiculum 

 is an invaginated secondary tube which becomes highly 

 chitinised it is difficult to understand how it can represent 

 a sternite, and the most we can say is that it arises from, 

 or near to the position of the ninth sternite, in the same 

 manner as the false spiculum, or strut, in Ithycerus and 

 Belus -arises from the edge of the eighth sternite. Apodemes 

 (similar to the spiculum in origin (invaginations of the 

 ectoderm) arise in various parts of the body in insects and 

 do not represent a sternite or a tergite, and occur in positions 



