356 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



to the dorsal epipodial nerve, so that the resulting nerve, 

 we pointed out, possesses both pedal and pleural elements. 

 Pelseneer v^hile admitting the junction of the two nerves, 

 denies that the fibres pass from one to the other. In 

 a brief account of the nervous system of Phyllirhoe 

 hucephalum he describes and figures a branch from " le 

 nerf palleal " (epipodial nerve), which comes in contact 

 with a dorsal pedal nerve, and forms with it a plexus, 

 but with only a simple juxtaposition and without any 

 interchange of fibres. In a footnote* he says ''La meme 

 chose s'observe dans I'autres Tritoniens ; par example 

 Dendronotus, ou Herdman et Clubb I'ont signalee, con- 

 cluant de ce fait que des fibres pedieiises passent dans le 

 nerf innervant les papilles dorsales. Or je me suis assure 

 que chez Dendronotiis, comme chez PJiyllirhoe, il y a 

 simple juxtaposition locale des deux nerfs." He again 

 refers to it in similar language in a subsequent paragraph 

 dealing generally with the innervation of the dorsal 

 appendages. 



It is obvious in a point like this in which the course of 

 the individual fibres of the nerve is concerned, that the 

 microscopic examination of thin serial sections with high 

 powers of the microscope is absolutely necessary, and that 

 it is impossible to determine it satisfactorily by means of 

 promiscuous sections or dissection only. It is somewhat 

 difficult to obtain sections in a perfect condition of 

 the region where this plexus is placed, owing to the 

 proximity of the odontophore, the radula of which is apt 

 to tear and destroy the sections, unless the animal has 

 been killed without undue contraction so that the odonto- 

 phore lies in its more normal position, in front of the 

 plexus. I have been fortunate enough, however, to 

 obtain a series in which it is possible to trace the course 



* Loc. cit., p. 42. 



