Literary Notices. ix 



and convincingly than has hitherto been done. Reviewing the devel- 

 opment of our knowledge in the gradual exclusion of the Vth from the 

 innervation of the lateral line organs, he points out that the scheme of 

 their innervation given by him {vide supra) has been shown to apply to 

 all classes in which the lateral line system exists, if we take the most 

 careful researches as a guide e. g. Holocephali (Cole), Elasmobranchs 

 (Ewart), Teleosts (Pollard — Siluroids e. g. Clarias, and Auchenaspis 

 and we should now add Herrick's researches on Menidia as most con- 

 clusive of all as to the condition in Teleosts), Ganoids (Allis), Dipnoi 

 (Pinkus) and Amphibia (Strong). He summarises the proofs that ''the 

 lateral line system is a distinct formation innervated by a single and 

 specially developed system of nerves " as follows : 



(i) Their distinct and characteristic development from the skin 

 and not " like the true cranial nerves " from the neural crest (Pollard, 

 Beard, Froriep, Kupffer). 



(2) The development of the canal organs by the splitting of a 

 single organ (Beard). 



(3) The total disappearance of the lateral line nerves when the 

 organs disappear, as in the metamorphosis of the frog (Strong). 



(4) " The tendency on the part of the lateral hne nerves to arise 

 both in the embryo and in the adult by the splitting of a single trunk" 

 (Amphibia — Strong, Siluroids — Pollard, Elasmobranch embryos — Van 

 Wijhe, Beard, Laemargus — Ewart). It may be remarked here, as Cole 

 points out in a later paper,^ that this condition is often secondary. 



(tj) The common origin (or rather terminus or center) of the lateral 

 line nerves in the brain. 



(6) The fact that each lateral line nerve has its own ganglion dis- 

 tinct from the ganglion of the cranial nerves scnsu strictu. 



The grounds above adduced by Cole are of great strength and 

 establish a strong presumption against apparent contradictions such as 

 are found in the description of the innervation of canal organs in cer- 

 tain cases by other nerves than those of the lateral line system. Such 

 exceptions obviously require a careful consideration and this Cole de- 

 votes to two of these cases which have been apparently clearly ob- 

 served. The first is the case, observed by Cole himself, of the inner- 

 vation of two sense organs of the supra-orbital canal by twigs from the 

 profundus. Cole thinks, very properly, that we may assume here on a 

 priori grounds, and pending a complete microscopical examination, that 



' Reflections on the Cranial Nerves and Sense Organs of Fishes. Trans. 

 Liverpool Biological Soc, Vol. 12, 1898, 



