360 



THE ANATOMY OF FNVERTEBRATED ANIMALS. 



to be seen. Behind the junction of the oviducts with the 

 vagina and the last abdominal ganglion which lies upon the 

 latter, there is a small sac with a long neck from which a short 



Fig. 101.— Blatta orientalis.— Female genital organs : a, the posterior abdominal 

 ganglion ; 6, the oviducts ; c, d, e, the ovarian tubes ; /, the filament by which 

 their extremities are united ; g, the spermatheca ; h, the colleterial glands. 



cascal process is given off. It has a thick chitinous lining and 

 a muscular investment, and is the spermatheca. Behind it 

 are two large, ramified, tubular colleterial glands, which prob- 

 ably give rise to the substance of which the egg-case is 

 formed. Their conjoined ducts open behind the spermatheca. 

 The eggs are inclosed, sixteen together, in strong capsules 

 of a horny consistency, shaped somewhat like a cigar-case, 

 and presenting a longitudinal slit, the raised and serrated edges 

 of which are closely applied to one another. It is through 

 this slit that the fully-developed young make their exit. The 

 eggs attain one-sixth of an inch in length. Each has its own 

 thin but tough brownish shell, the surface of which is beauti- 

 fully ornamented with hexagonal patches of minute tubercles. 

 They are arranged parallel with one another in two opposite 

 series, one series occupying each half of the case. The eggs, 

 adapting themselves to the form of the case, are convex out- 

 ward and concave inward, and thus, though their ends touch, 

 a median space is left between the two sets. The inner con- 

 cave face of the egg is that on which the sternal face of the 

 embryo is situated. The female carries the egg-case about 



