1911] Watson: The Genus Gyrocotyle. 413 



anterior bridge commissure is given off and reaching their great- 

 est size in that region. Anteriorly they pass into the anterior 

 longitudinal stems, extending fully a third of the total distance 

 from the commissure to the anterior ring. Prom each ganglion 

 the following branches are given off (pi. 36, fig. 27 ) . 



1. An anterior lateral nerve stem, a prolongation of the 

 anterior nerve stem in front of the anterior bridge commissure, 

 runs forward along the dorso-lateral margins of the acetabulum. 

 From these stems there are given off dorsal, ventral and lateral 

 branches to the body musculature, and median branches to the 

 outer coat of the acetabular muscles. Certain branches from the 

 dorsal surface run forward, to the dorsal sensory ridges later 

 described, and from the ventral surface of each stem near its 

 anterior extremity a large nerve runs forward vent rn laterally to 

 the sensory pits on the ventral serface. At the anterior extremity 

 of the worm near the acetabular opening, each lateral nerve stem 

 divides into two branches which pass, one ventrad, the other 

 dorsad, at right angles to the longitudinal stem. These nerves 

 break up in the median line to form the anterior nerve ring. 



2. Four nerves are given off from the ventral surface of the 

 knot, two of which are directed posteriorly and two anteriorly. 

 The posteriorly directed pair of branches are distributed to the 

 follicles of the testes (test, n., pi. 36, fig. 27). The anteriorly 

 directed pair pass around the posterior margin of the acetabulum 

 on its ventral surface and send out branches on this surface. 



3. Four nerves arise from the dorsal surface, running for- 

 ward and laterally into the inner longitudinal muscles. 



4. Two nerves arise from the lateral surface of the ganglion, 

 one running forward and ventrally, the other towards the dorsal 

 surface, into the central musculature of the body and the vitel- 

 laria. 



5. Several nerves are given off from the anterior face of the 

 ganglion and run forward along the surface of the acetabulum 

 to innervate the outer meridional acetabular muscle coat (the 

 homologue of the inner longitudinal coat of the body muscula- 

 ture). 



The Anterior Ring Commissure. — The anterior end of the 

 worm is pierced by a round opening into the cavity of the 



