REPRODUCTION. 175 



single organ ; (2) long coiled vasa deferentia, opening into or 

 close to (3) paired vesiculce seminales, which discharge into 

 (4) the ejaculatory duct, a muscular tube, with chitinous lining, 

 by which the spermatozoa are forcibly expelled. Opening into 

 the vesiculce seminales, the ejaculatory duct, or by a distinct 

 external orifice, may be found (5) accessory glands, very 

 variable in form, size, and number. More than one set may 

 occur in the same Insect. To these parts, which are rarely 

 deficient, are very often appended an external armature of 

 hooks or claspers. 



The male Cockroach will be found to agree with this 

 description. It presents, however, two peculiarities which are 

 uncommon, though not unparalleled. In the first place the 

 testes are functional only in the young male. They subsequently 

 shrivel, and are functionally replaced by the vesiculse seminales 

 and their appendages, where the later transformations of the 

 sperm-cells are effected. The atrophied testes are nevertheless 

 sufficiently large in the adult to be easily made out. Secondly, 

 the accessory glands are numerous, and differ both in function 

 and insertion. Two sets are attached to the vesiculae seminales, 

 and the fore end of the ejaculatory duct (ntriculi majores and 

 breviores) ; another large conglobate gland opens separately to 

 the exterior. We shall now describe the structure of these parts 

 in more detail.* 



The testes may be found in older larvae or adults beneath 

 the fifth and sixth terga of the abdomen. They lie in the 

 fat-body, from which they are not very readily distinguished. 

 Each testis consists of 30-40 rounded vesicles attached by 

 short tubes to the vas deferens.f The wall of the testis 



We propose to notice here the chief differences which we have found between 

 the figures of Brehm (loc. cit.), which are the fullest and best we have seen, and our 

 own dissections. 



Figs. 10, 11 (pp. 169-70). The ejaculatory duct and duct of the conglobate gland 

 are made to end in the penis (infra, p. 178). 



Figs. 14, 15 (p. 173). These figures seem to us erroneous in many respects, such 

 as the median position of the penis and titillator. 



Fig. 16 (p. 174). The pair of hooks marked E are too small, and there are additional 

 plates at the base, which are not figured (see our fig. 102). F (of our fig.) is 

 omitted. 



f In Blatta yermanica the testes are functional throughout life. They consist of 

 four lobes each. The vasa deferentia are much shorter than in P. orientalis. 



