578 TEXT-BOOK OF ENTOMOLOGY 



septum, but seems iu later stages to have no longer an intimate 

 connection with it. 



The formation of the single ovarian tubes, which in Phyllodroinia 

 number about 20, is accomplished by the extension of indentations 

 from the dorsal side towards the ventral side of the ovarian rudi- 

 ment (Fig. 550). At the same time the epithelial cells (ep), which 

 were originally situated in part between the genital cells, become 

 arranged in the form of an epithelium on the surface of the ovarian 

 tubes, which soon forms on its outer surface a structureless cuticular 

 tunica propria. The outer peritoneal membrane of the ovary be- 

 comes formed of the cells of the surrounding tissue of the fat -body. 



The genital rudiment originally extends, as already stated, from 

 the 2d to the 7th abdominal segment. In the last, however, the 

 genital cells at first occur only sparingly, and afterwards completely 

 disappear, so that here the genital cord appears composed of epi- 

 thelial cells only. This part is the rudiment of the oviduct proper, 

 and forms a direct continuation of the above-mentioned cell-cord 

 which is situated ventralward from the genital cells, from which, 

 as we have seen, the proximal cup-shaped section of the oviduct is 

 formed. The hinder section of the oviduct turns down ventrally in 

 order to unite at the boundary between the 7th and 8th abdominal 

 segments with the hypodermis. The rudiment of the oviduct origi- 

 nally forms a solid strand of cells. Afterwards a cavity is formed 

 by the separation of the cells. 



In later stages there is a considerable shortening of the genital rudiment, so 

 that it occupies a smaller number of abdominal segments than at first. At the 

 same time the single ovarian tubes pass out of their originally vertical position 

 into one more horizontal. 



The paired connections of the rudiments of the oviducts with the 

 hypodermis of the intersegmental furrow between the 7th and 8th 

 abdominal segments reminds us of the conditions in the Ephemeridae. 

 This is the primitive condition in insects. In the female of Phyllo- 

 droinia there is developed during larval life, from an ectodermal 

 invagination, an unpaired terminal section of the genital passage, 

 which becomes the genital pouch in which the egg-case (ootheca) 

 is held. This genital pouch is formed, as Haase has already proved, 

 by the withdrawal of the chitinous ventral plate of the 8th and 9th 

 abdominal segment by invagination into the interior of the body. 



The development of the efferent passages has been investigated 

 by Nusbaum in the cockroach (Periplaneta) and in the Pediculina. 

 He found that only the vasa deferentia and the oviducts arise from 

 the hinder cord of the germs of the sexual glands, that is, out of 



