THE CRANIAL NERVES AND LATERAL SENSE ORGANS OF FISHES. 130 



Shore, in 1889, applying Gaskell's methods to the fishes, arrives at some noteworthy 

 results. He states tliat the vagus is mostly composed of the visceral elements of the 

 anterior spinal nerves rather than a compound of several complete metameric nerves, as 

 Gegenbanr maintained in his memorable Rexanclnts * paper. Shore discovered on the 

 dorsal branch of the vagus a small ganglion which he homologises with a doi-sal root or 

 " somatic sensory" ganglion f- At the most, however, it can only represent a portion of 

 this ganglion. The branchial (= post-branchial) ganglia ai-e considered to represent the 

 vertebral or vagrant ganglia of the syrapathethic trunk, and the proe-branchial ganglia 

 (first described by Shore) the proe-vertebral or collateral ganglia of the sympathetic 

 system. The latter statement will be discussed later on, but I may mention now that 

 Shore admits the fibres which join the prse-branchial ganglia should be non-meduUate, 

 which the prae-branchial fibres are not. Omitting the dorsal branch and its ganglion, the 

 vagus, according to Shore, contains the sympathetic elements only of a spinal nerve, and 

 not its somatic elements. He further states that the post-branchial nerve contains some 

 splanchnic sensory fibres, and believes finally with Habrecht that the lateralis lateral line 

 nerve is equivalent to the lateral strands of the Nemertea — a conclusion which our 

 knowledge of the lateralis nerve enables us absolutely to disprove. 



Ayers (1892, 7), referring to the -chorda tympani of Mammals, a subject which we 

 shall see later on interests us in this connection, says (pp. 312-313) : — " As is well known, 

 the sensory fibres subserving the sense of taste in the anterior two-thirds of the tongue 

 run through the chorda tympani, and the recent investigations of Sajiolini make it fairly 

 certain that the chorda tympani is a continuation of at least a portion of the fibres of the 

 portio intermedia Wrisbergi, which pass through the ganglion genicali to the chorda 

 tympani." 



Ewart (1893, 70), after referring to the small size of the cells in the ciliary ganglion 

 (see, re size of cells in facial ganglion, below), says, in. describing the palatinus facialis of 

 Elasmobranchs, that it " dips downwards and In-eaks up into numerous branches, which 

 end in the mucous membrane of the roof of the mouth. At the root of this trunk there 

 are always numerous ganglion cells. Sometimes these cells are continuous with the cells 

 at the root of the facial trunk ; but in others they extend a short distance into the root 

 of the palatine, and are completely, or all but completely, separated from the ganglion of 

 the facial trunk. I have no hesitation in saying that the palatine nerve of the skate 

 corresponds, as has been suggested by Gegenbaur and othei's, to the great superficial 

 petrosal of the mammal, and that further enquiries are likely to show that the ganglion 

 at the root or in the trunk of the palatine nerve corresponds to the spheno-palatine 

 (Meckel's) ganglion of the mammal. Or, to put it another way, were a spheno- 

 palatine ganglion developed in the skate, it would be derived from the cells (or some of 



* Cp. Minot (140, pp. 650-651). Whether formed of complete metameric nerves or not I do net propose to 

 discuss, but that the vagus is a compound nerve is not a " bold hypothesis " but an anatomical fact, lack of 

 embryological evidence notwithstanding. 



t An omission in my Chimcera paper (46) may be corrected here. On p. 671, line 15, for " is in connection,'' read 

 " is also in connection.'' 



SECOND SERIES. — ZOOLOGY, VOL. VII. 20 



