1915] Muir — The Ontogeny of the Genital Tubes in Coleopiera 151 



fore of ectodermic origin. The spermatheca arises from the azygos 

 or uterus. 



Conclusions. 



My studies of the ontogeny and anatomy of the male genital 

 tube in Coleoptera lead me to the following conclusions: those 

 relating to the internal sac naturally do not apply to those forms 

 where it is not differentiated. 



The oedeagus arises as a tubular organ at the base of an interseg- 

 mental invagination between the ninth and tenth sternites. By 

 transverse folds it differentiates into three sections: a basal or outer 

 section (tegmen), a median segment (median lobe) more or less sur- 

 rounded by the tegmen, and a distal segment (internal sac), which 

 is generally invaginated within the median lobe. Cases occur in 

 different families in which each of these segments is reduced or 

 absent. 



There is no evidence that one or more sternites take part in the 

 composition of the oedeagus ; the only sternite that could do so is 

 the tenth, but it is more likely that this becomes dechitinized 

 (except in Enarsus) and incorporated into the anal tube or the 

 second connecting membrane. 



No tergite takes part in the composition of the oedeagus. 



Where the ninth sternite is well developed there is no spicule, 

 but it often has a pair of projections, or a single projection, from 

 its base, and the latter may be represented by the spicule in such 

 forms that have no ninth sternite. 



Figures la-e are diagrammatic, figures 2-9 are all drawn from 

 specimens with the aid of a camera lucida. 



EXPLANATIONS OF FIGURES. 



Fig. la to e. Diagrammatic representation of the development of the male 

 oedeagus. 



Fig. 2. Early stage of genitalia of cf pupa of R. obscnra. 



Fig. 3. Later stage of same. 



Fig. 4. Nearly mature stage of same. 



Fig. 5. Early stage of genitalia of c? pupa of Carpophilu.i humeralis. 



Fig. 6. Early stage of genitalia of o^ pupa of Cwlophora inaquaiis. 



Fig. 7. Later stage of same. 



Fig. 8. Lateral view of abdomen of Dcrmexies vulpimts. 



Fig. 9. Ninth segment of same. 



