The Lateral Sensory System in the Muraenidae. 139 



vinced, is also in accord with the supposition that the maxillary 

 labial furrow of Conger is a snpraniaxillarj^ one; Conger and Polj^pterus 

 thus agreeing- in the presence of this furrow associated with the probable 

 absence of a maxillary bone. In the other Muraenidae examined this 

 maxillary labial furrow is not found. The furrow in Conger has peculiar 

 relations to the infraorbital lateral canal, and it is because of this 

 that I have here so particularly referred to it. 



Certain general peculiarities of the lateral sensory canals of 

 Conger have been already referred to by Collinge. One of them is 

 the pouch-like form of most of the primary tubes of the system, this 

 being also a peculiarity of the tubes in the other Muraenidae. Another 

 is the enclosing of the sensory canals, beyond the limits of certain of 

 the bones, in a tubular structure of dense connective and fibro- 

 cartilaginous tissue, the related bones being apparently ossifications 

 of this tissue. This is probably also common to the other Muraenidae, 

 but I made no histological examination whatever of the tissues there 

 concerned, and the presence of cartilage in the tubular sti'uctures en- 

 closing the canals in the other Muraenidae, was not evident as it is 

 in Conger. Collinge says that tubes exactly similar to those of 

 Conger have been described by Leydig in Lota vulgaris, but I have 

 been unable to consult the work referred to. 



The pouch-like primary tubes of the lateral canals of Conger are 

 said by Collinge to be saccular dilatations of the canals themselves. 

 This is hardly a proper statement, for the pouches are in reality 

 dilatations of the primary tubes alone and not of the canals. Each 

 pouch is formed of a delicate layer of tissue, and usually lies on one 

 side onh^ of the canal to which it is related; though it may have a 

 short extension on the other side also. The pouch is almost invariably 

 covered externally by a dense, stringy, and peculiar connective tissue 

 which seems to have been developed in relation to and as a protection 

 for it. The i)0uch lies almost always at the level of the external, 

 superficial surface of the canal to which it is related, and it may 

 either open on the external surface of the head by a single primary 

 pore, usually placed at its out^r extremity, or have no related external 

 opening whatever, in which case it forms a blind sac. 



