THE OVARIES AND EGG-TUBES 



501 



and (3) the actual ovarian tube, or chambered main division, this 

 forming the longest part of the egg-tube. 



The slender terminal thread serves to attach or suspend each egg- 

 tube near the dorsal vessel (not directly to the heart, as formerly 

 supposed), becoming lost in the fat-body. 



The terminal chamber contains undifferentiated cell elements, sup- 

 posed to be the remains of the ovarian rudiments. From these arise 

 (either in the embryo or larva) first, the follicle epithelium of the 

 ovarian tubes; and, second, the material for the 

 formation of the new eggs, and nutritive cells. 

 " In the terminal chamber these cell-elements re- 

 main undifferentiated, excepting when required for 

 the removal of the follicle epithelium, eggs, and 

 nutritive cells in the adult insect." (Lang.) This 

 portion of the ovariole is called the germarium. In 

 Blatta it is filled with protoplasm in which nu- 

 merous small nuclei are imbedded. (Wheeler.) 

 The chambered main division of the egg-tube 

 contains the ripening eggs, one in each compart- 

 ment, the tube appearing like a string of beads. 



The egg-tubes are of two types : (1) those with- 

 out, and (2) those with nutritive cells, the first 

 kind being the simplest, and occurring in the 

 Synaptera (except Campodea) and in Orthoptera. 

 As an example may be cited that of the cockroach 

 (Fig. 473), where in each tube there is a simple 

 continuous row of eggs from the terminal cham- 

 ber to the oviduct. The tube being constricted 

 between these consecutive eggs, gives it a beaded 

 appearance. FIG. 473. Ovarian 



tube of P. orientalis : 

 A, section near the end ; 



In the cockroach (Periplaneta orientalis} each egg-tube JfJJjf 8 j JjJSStowi 

 has a beaded appearance. Its wall consists of a trans- down ; ec,, egg-cells in 

 parent elastic membrane, lined by epithelium, with an ^^|t* mber< ~ After 

 external peritoneal layer of connective tissue. The ter- 

 minal filament (tf) is filled with a clear protoplasm, with a few nuclei. In 

 the terminal chamber (tc) are large nucleated cells, with separate nuclei, 

 both entangled in a network of protoplasm. In the third, or egg-chamber 

 (ec), are about twenty ripening eggs, arranged in a single row. "Between 

 and around the eggs the nuclei gradually arrange themselves into one-layered 

 follicles, which are attached, not to the wall of the tubes, but to the eggs, and 

 travel downwards with them. As the eggs descend, the yolk which they contain 

 increases rapidly, and the germinal vesicle and spot (nucleus and nucleolus), 

 which were at first plain, disappear. A vitelline membrane is secreted by the 

 inner surface and a chitinous chorion by the outer surface of the egg-follicle. 



