THE CRANIAL NERVES AND LATERAL SENSE ORGANS OF FISHES. 133 



The first author to recognise the important hearings whicli the lateral line system 

 might possibly have on the morphology of the skull was, I helieve, Dr. Traquair 

 (1865, 207), who, as I have previously pointed out, made considerable and skilful use of 

 the relation of tlie two structures in solving the problem of the asymmetrical skull. 

 Sagemehl (1883, 170), writing independently of McMurrich, says*: — "I desire to 

 mention, at this jioint, tliat hitherto the relations of the mucous canals to the bones of 

 the cranium have hardly been given a thought, and yet they deserve a closer study, as 

 these relations are very constant, and in questionable cases they can be used to determine 

 doubtful homologies." Allis (1889, 4) points out (p. 46i) that "it is only within the 

 last five or six years that the constant relations of the cranial canals to the dermal bones of 

 the head, and their imj)ortance in determining these bones in doubtfid cases, have been 



recognised. Both Sagemehl and Van Wij he have called special attentioi: to this " 



Since 1883, Sagemehl, Bridge, and numerous other authors have, when dealing with 

 the skull of bony fishes, also described the cranial sensory canals, with the result that the 

 relations of the lateral canals with the skull have been shown to be remarkably 

 constant. Hence the table given above may be said to represent the facts in most 

 bony fishes. 



I. The Trigejiino-facial Ganglionic Complex. 



General Statement. — As it is impossible to arrive at an accurate appreciation of this 

 complex by observations on the adult, the following description has been based upon a 

 study of sections of young forms. The trigemino-faeial ganglion in these sections is 

 seen to consist essentially of three portions arising by two roots, which are from above 

 downwards : — 



(1) A Lateral line ganglion. Consists of two parts united in front, one being situated 



ventral to the other. The dorsal part gives rise to the superficial ophthalmic 

 and buccal lateral line nerves, which arise as a single trunk and separate into 

 superficial ophthalmic and buccal trunks as a passage is made through the second 

 portion of the trigeraino-facial ganglion. The ventral portion is doubtless connected 

 with the external mandibular lateral line nerve. 



(2) A " Trigeminal " or "Gasserian" ganglion t- This is situated internal and largely 



anterior to the second or ventral portion of (1). From this portion of the 

 complex the superficial ophthalmic of the trigeminus, the maxillo-mandibular 

 trunk, and, probably, the post-branchial division of the facial arise. If the latter 

 statement be cori'ect, as seems certain, this ganglion should be called the 

 " trigemino-faeial." 



(3) A "Facial" ganglion. This is a long and perfectly distinct ganglion which lies 



ventral to (2). It is connected with the palatine nerves and also with the 



* English translation by Shufeldt, p. 75i! (188.5, 1S7). 



t I have called this ganglion the " trigeminal "' or " Gasserian " in order to distinguish it from the " facial "' 

 ganglion. The question of the latter is discussed liclow. It id sufficient to remark here that were it more distinctively 

 a ganglion of a cranial nerve, and less a sympathetic ganglion, the morphology of the "trigeminal" ganglion would 

 doubtless be less ditficult to decide. 



19* 



