240 W. HAROLD LEIGH-SHARPE 



the containing siphon sac (s) in an anteroposterior direction, but 

 no erection of the claspsr. 



2. A series of successive stimuh to the posterior branch of the 

 52nd spinal nerve causes prolonged spasmodic secretion, and the 

 sudden activation of secretion from hitherto dormant papillae, 

 but no contraction. During sustained stimulation contraction 

 appears to be inhibited. On the cessation of stimulation a 

 similar undulating contraction of the siphon sac follows. After 

 prolonged stimulation there may be from two to as many as six 

 such contractions following one another at gradually lengthen- 

 ing periods. 



3. Stimulation of the posterior branch of the 54th spinal nerve 

 causes erection of the clasper which continues for fifty seconds, 

 the clasper continuing to remain erect during, and for some 

 time after, a series of successive stmiuli, but no secretion or sac 

 contraction. 



4. If the posterior branch of the 52nd spinal nerve be severed, 

 and the common portion of this spinal nerve be stimulated, 

 movements of the pelvic fin follow, but no secretion or sac 

 contraction. 



5. If the spinal cord be stimulated between the origin of the 

 52nd and 54th spinal nerves (and, indeed, at other places, in which 

 cases other responses occur), secretion, followed by sac contrac- 

 tion, and clasper erection supervene simultaneously; wherefore, 

 in order to obtain perfect results in cases 1 and 3, it is better to 

 sever the spinal cord between the origin of the 52nd and 54th 

 spinal nerves. 



6. Besides being distributed to the accessory structures of the 

 clasper, such as the signal, etc., the posterior branch of the 54th 

 spinal nerve also gives off prominent branches to the muscles 

 that work the whole clasper, such as the one indicated at A' 

 (fig. 17). If these branches are not cut, stimulation of the whole 

 posterior branch causes not only erection, in the sense of that 

 word as previouslj^ used, but also flexion of the clasper in an 

 anterior direction, exactly as would be required in copulation. 

 If these secondary branches be severed, stimulation of the main 

 branch still causes erection, but in not so complete and perfect a 



