THE COCKROACH. 359 



its dilatation. On the sternal side of the mushroom-shaped 

 gland, between it and the last abdominal ganglion, there is 

 an accessory gland composed of dichotomous monilated tubes, 

 lined by a columnar epithelium, all bound together by a com- 

 mon investment into a flattened elongated mass. 



As the duct of the mushroom-shaped gland in the adult 

 male always contains spermatozoa, and no other organ con- 

 taining spermatozoa is to be found, this gland has naturally 

 been taken for the testis. Rajewsky, 1 however, has recently 

 pointed out that the true testes are situated in the tergal 

 region of the abdomen, and that they may be found in this 

 region in the young and yet wingless males, though they are 

 much obscured by the corpus adiposum which invests them. 

 He traces the efferent duct of the testis to the glands just 

 mentioned. In the adult male the testes atrophy, and are 

 hardly to be discovered among the masses of the corpus adi- 

 posum. I have found the testes in the young males in the 

 position assigned to them by Rajewsky. They consist of 

 numerous oval or pyriform sacs attached by short pedicles to 

 a common duct. 



The ovaries (Fig. 101) are two groups of eight tubes, sit- 

 uated on each side of the hinder half of the abdomen. The 

 ovarian tubes, or ovarioles, of each group communicate with 

 a short oviduct, which soon unites with its fellow in the mid- 

 dle line and opens externally by the very short and wide 

 vagina. The finely tapering anterior ends of the ovarioles 

 of each side are continued forward by delicate cellular pro- 

 longations. These finally unite together into one long fila- 

 ment, which can be traced for some distance forward among 

 the lobes of the corpus adiposum. It is a cellular cord, which 

 appears to be nothing but a process of the mesoderm. Nu- 

 merous nucleated cells, from some of which the ova take their 

 origin, while others remain as interstitial cells, which are 

 eventually converted into an epithelium, make up the sub- 

 stance of the slender anterior terminations of the ovarioles. 

 The ova situated behind these enlarge, and become disposed 

 in a single series. Further on, the epithelial cells form a thick 

 stratum round each egg, and possibly assist in the formation 

 of the large vitellus with which it is ultimately provided. As 

 the egg advances toward maturity, the vitellus acquires first 

 a finely and then a coarsely granular structure, and the ger- 

 minal vesicle and spot, previously conspicuous, are no longer 



1 Hofmann and Schwalbe, " Jahresbericht," 1875. The original paper is 

 in Russian, and I have not seen it. • 



