42 



a similar structure, though slightly different in detail, being a little 

 shallower, and of greater lateral extent. There are the same branched 

 hairs present in their interior as in P. orientalis and P. americana. 

 But there is in this species an additional gland , opening by a tubular 

 duct under the intersegmental membrane between the fifth and sixth 

 terga above the glandular pouch of each side, and extending forward 

 into the body cavity. The gland and its duct are proliferations of the 

 hypodermis, and there is no invagination of the cuticle. 



It is in Blatta germanica that the greatest complication of struc- 

 ture occurs. In this species there appears to be no trace of the organ 

 in the female. But in the male it is relatively of enormous size, ex- 

 tending over the sixth and seventh somites, as well as projecting far 

 into the body cavity ; it is quite visible externally in the ordinary con- 

 dition of the animal. 



An external view of the dorsum of the abdomen of the male shows 

 the following peculiarities. The first four terga are alike and unmodi- 

 fied. The fifth is slightly larger and marked by a transverse furrow, 

 deepest towards the middle line. The sixth is much larger, and shows 

 two very large, oval depressions of considerable depth, separated from 

 one another by a median septum. Each of these depressions is further 

 divided in two by a transverse ridge, which is broad and shallow towards 

 the lateral edges of the tergum, but becomes narrow and deep towards 

 the middorsal line where the ridges of either side are confluent and pro- 

 duced into a rod or cirrus, which projects freely upwards from the sur- 

 face of the tergum. The depressions with their ridges extend nearly 

 to the extreme lateral edge of the tergum. 



The seventh tergum is still larger than the sixth and emarginate 

 in the middle line posteriorly. Close under the projecting edge of the 

 sixth tergum it shows a large median opening divided in two by a 

 median longitudinal septum which does not quite reach the level of the 

 surface of the tergum. Externally these openings do not reach more 

 than a third of the way from the middorsal line to the lateral edges of 

 the tergum. Sections show that these two openings lead into large 

 tubular invaginations of the cuticle and hypodermis which extend in- 

 wards in a postero-lateral direction to end blindly close to the stigmata 

 of the sixth somite. 



The following points of structure and histology can be readily 

 made out from sections. All the depressions and invaginations are lined 

 by a tough brown cuticle of some thickness. Over the ridge and cirrus 

 it differs from the rest in being thinner and staining red with borax 

 carmine. It is noticeable, however, tliat the foliate expansions of the 

 10^'' tergum in the males of Blatta germanica and Periplaneta ameri- 



