BLATTA. 229 



three to form the subcesophageal mass, and the fusion of the last five to 

 form the terminal abdominal ganglion. As in the loloster, the first two 

 ganglia move forwards to the brain and the jaw-ganglia fuse together. 



In the cockroach there is no trace of excretory glands 

 opening at the base of any of the appendages, 

 xcre ory. ^ different kind of excretory organ is found in 

 the Malpighian tubules described above. 



The IrachecE are tubes, lined with chitin, thickened in a 

 spiral, and passing inwards from the stigmata. They branch 

 . all over the body and pass into the wings. They 



appear in dissection like delicate silver tubes. In 

 a general way, there pass inwards from each stigma a dorsal, 

 a ventral and a splanchnic branch. The dorsal branches 

 anastomose beside the heart, the ventral anastomose near 

 the nerve-cord, and the splanchnic branch all over the vis- 

 cera. The first stigma sends two large paired tracheae 

 forwards to supply the head. 



The male organs consist of a pair of minute testes in the 

 dorsal part of the middle of the abdomen. They lead by 



_, ... small vasa deferentia into a " mushroom-shaped 



Reproductive. , , ,, :; , 1 • i • n • j 



gland, a tufted organ which is really a paired 



vesiculum seminalis ; an ejaculatory duct passes from these to 

 the exterior. 



In the female each of the y^zxxtdi ovaries consists of eight 

 long tubes or ovarioles. They unite to form a pair of 

 oviducts which open together on the 8th sternon. The 

 short united portion is sometimes called the uterus. A 

 pair of branched colleterial glands open into the uterus and a 

 small sac or spermatheca opens on the 9th sternon. In 

 both sexes there are gonapophyses or paired sclerites, modi- 

 fied to assist reproduction — in the male for copulation, in the 

 female for deposition of the ova. In the female the 8th 

 and 9th sterna are telescoped within the large 7th, 

 producing a genital pouch. It should be noted that the 

 female opening, as in the lobster, is two segments anterior 

 to that of the male. 



The eggs are laid in a capsule (one from each ovariole, making 

 sixteen in all) formed by the colleterial gLandi>. They have much yolk, 



and the segmentation is equal and superficial. A 7)entral 

 De7elopineiit.//(CZ/^ is produced by a thickening of the cellular layer. 



This is invaginated, the walls meeting above and forming 

 an amnion, a remarkable protective membrane, found also in land 



