XXI] 



URINO-GENITAL SYSTEM 



539 



Urino-geni 

 tal organs. 



The first spinal nerve comes out from behind the first vertebra and 

 is called the hypoglossal ; it runs 

 directly to the respiratory muscle, the 

 mylohyoid, crossing the vagus and 

 glossopharyngeal in its course. At 

 the sides of the dorsal aorta the two 

 chains of sympathetic ganglia 

 can be made out, connected by cross 

 branches with the spinal nerves. 

 To turn now to the excretory 



system, the kidney 



can be seen when the 



alimentary canal is 

 removed. It is a long narrow strip 

 on each side adjacent to the aorta. 

 In front it tapers to the merest 

 thread, but behind, close to the 

 cloaca, it thickens somewhat. Along 

 its outer edge runs the archinephric 

 duct, and external to the archi- 

 nephric duct is situated the long 

 oviduct. 



The tubules which compose the 

 kidney retain throughout life the 

 ciliated openings into the body- 

 cavity, and if the narrow part of 

 the kidney be cut off and mounted 

 in a little salt solution it is possible, 

 at least in small specimens, under 

 a low power of the microscope, to 

 see the funnels and to observe the 

 whirlpools due to the currents pro- 

 duced by their cilia. 



The genital gland in both sexes 

 is represented by a pair of ridges 

 suspended to the inner edges of 

 the front parts of the kidney by 

 slings of peritoneum similar to the 

 mesentery suspending the gut, and on 

 this account called mesenteries. 

 In the female the oviduct opens 



FIG. 264. Urine-genital organs of 

 a female Molge cristata x about 5. 



1. Ovary. 2. Bemnant of vasa 

 efferentia. 8. Kemnant of longi- 

 tudinal canal connecting the vasa 

 efferentia. 4. Sexual portion 

 of kidney. 5. Archinephric 

 duct. 6. Oviduct. 7. Pos- 

 terior non-sexual portion of 

 kidney. 8. Opening of archi- 

 nephric duct. 11. Internal open- 

 ing of oviduct. 12. Suspensory 

 ligament. 13. External open- 

 ing of oviduct. 



