i64 COMPARATIVE ANATOMY 



saccular vesiculse seminales lying side by side, and bearing at 

 their anterior ends a dense tuft of finger-shaped diverticula. 

 In the adult male these diverticula are filled with spermatozoa 

 and are of a glistening white colour : they were long mistaken 

 for the testes. The vesiculse seminales receive the sperm-ducts 

 on either side and posteriorly unite to form a muscular tube, 

 the ductus ejaculatorius, which opens into the genital pouch 

 by the male pore. The complex apparatus of hooks and plates 

 surrounding the genital pore has already been mentioned. 

 On the lower side of the ductus ejaculatorius is the so-called 

 conglobate gland, the function of which is doubtful. 



The female organs consist of a pair of composite ovaries 

 communicating by short and rather wide oviducts with a very 

 short median uterus which opens into the genital pouch by 

 a slit-like aperture, the vulva, through the eighth abdominal 

 sternum. On its under side the uterus receives the duct of a 

 much ramified coUeterial gland, and just above the opening 

 of the vulva into the genital pouch is the orifice of a small 

 tubular spermatheca which is filled with spermatozoa by the 

 male during copulation. Each ovary consists of a bunch of 

 eight egg-tubes, distended at their posterior or oviducal ends, 

 but tapering gradually forwards to a point where their dia- 

 meters suddenly diminish. From this point the tubes are 

 continued forwards as narrow threads which unite to form a 

 single filament running forward till it is lost in the fat-body. 

 The thread-like upper end of each tube contains a mass of 

 granular protoplasm in which numerous nuclei are imbedded. 

 At the point where the thread suddenly expands to form the 

 tube the nucleated mass of protoplasm divides into a number 

 of large cells or primitive ova entangled in a network of proto- 

 plasm containing many nuclei. As these cells are passed down 

 the tube they become arranged in a single row, and each is 

 invested by a follicle consisting of a single layer of cells derived 

 from the nucleated network. During their descent the ova 

 increase very much in size, being distended with food-yolk 

 elaborated by the follicular cells, and they bulge out the walls 

 of the egg-tube so that the latter looks like a string of beads. 

 When ripe the ova are elongated oval, something like a sausage 

 in shape, with a shght flexure towards what will be the ventral 

 side of the embryo, and are surrounded by two membranes, an 

 inner or vitelline membrane secreted by the ovum itself, and 



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