370 EDWIN S. GOODRIOU. 



together, closely bound to each other and to the skeleton by 

 the connective tissue which surrounds them, it is difficult to 

 establish, without the possibility of doubt, that the contraction 

 is restricted to two radial muscles only. Nevertheless, after 

 repeated trials, I am quite convinced that such is really 

 the case. There can be no doubt whatever that the con- 

 traction does not spread to several neighbouring 

 muscles. 



If all the nerves, excepting one or two, are severed from 

 the spinal cord, and if then a general stimulation be induced 

 through the cord, only those pairs of muscles contract which 

 correspond to the one or two nerves left intact. 



The following experiment was also repeatedly made to 

 determine whether the nerve-supply of neighbouring segments 

 overlaps. Three consecutive nerves of the plexus. A, B, and C, 

 were severed from the spinal cord. The two outer ones, A 

 and C, were then excited by constant application of the 

 electric stimulus until the corresponding pairs of radial 

 muscles scarcely, if at all, responded. Then the middle nerve 

 B was stimulated, and its muscles were found to respond in 

 perfectly normal fashion. They contracted equally well 

 whether the outer nerves were still being stimulated or not. 

 This seems to me to prove, without the possibility of doubt, if 

 not that there is no overlap whatever, at all events that it can 

 only be very slight. 



So clear and definite was the evidence derived from these 

 and other experiments of a like nature, that I have no hesita- 

 tion in stating my opinion that each pair of radial muscles 

 (containing two dorsal and two ventral elements) derived 

 from a single segment, is supplied exclusively with motor 

 fibres from the ventral root of the nerve belonging to that 

 same segment. In fact, no plexus exists in the pectoral fin 

 of Kaja in the sense of a mixture or overlapping of the areas 

 supi)lied by the segmental motor nerves. 



So far as experiments were conducted on the pelvic fins 

 they gave the same results. 



Unfortunately, the dursal iins of Scylliuni tlo nut k-nd them- 



