INTRODUCTION. 



17 



(Hyinenoptera) ; or tlie last abdominal segments, which then are thin 

 and elongate, and may be telescoped, serve in this capacity (Diptera 

 and others). The chorion is often very hard, frequently covered with 

 a delicate and regular sculpturing, and always provided with one or 

 more openings, the micropyles, through which the spermatozoa may 

 enter. The outer form of the eggs varies : it may be spherical, oval, 

 discoid, rough, stalked, &c. 



" The male genitalia are for the most part a repetition of those of 

 the female. There is a pair of testes, each consisting of several long 

 seminal tubes or shorter seminal pouches, situated at the end of the 



Fig. 21. — Male genital or<jai}S afthe cackclwfcr (penis not drawn). 



h, vesicnla seminalis; g, vas deferens; k, glandular appendages; r, widened region of the 



duct of the same ; t, testis, consisting of six seminal pouches. (Alter Boas.) 



vas deferens. The two vasa deferentia unite to form a single duct, 

 which opens in a similar position to the vagina of the female. Each 

 of the vasa deferentia widens posteriorly to form a vesicula seminalis. 

 Special glandular appendages frequently open into these ducts, or into 

 their common portion. There is a more or less complicated copu- 

 latory organ, an evagination of the body wall, through which the 

 terminal portion of the seminal duct is continued, and capable of 

 partial or complete retraction when not in use. In many it may 

 possess hard chitinous portions, and lies hidden within the cloaca, 

 from which it may be protruded during copulation. " ^ 



1 Text-book of Zoology by Dr J. E. 

 B 



pp. 242, 243. 



