1092 



SCAXDINAVIAX FISHES. 



(lorsiil side, oiir ]i;iir (ni the dutsidc of the preorMtal 

 cartilage (oa) .■iiid annthcr (iiitside the spiracle {lii/a). 

 Asvininetrical capsules also occur, as in Tri/(/oii l)et\veeii 

 the anterior ends of the two nostrils. Thr anipullarv 

 canals e.xteiid throughout the sides of the body, those 

 of the ])ectoral tins for example, which run to the 

 hyoid capsules, attaining a considcral)le length (tig. .309). 

 In the IClectric Piays FKrrscii" has observed a regular 

 alternation on the dorsal side of the pectoral fins be- 

 tween tlie ducts of the auipulhe and those of the lateral 

 canal proj)er, the outer (distal) part and the oritice of 

 eacli anipullar\' duct lying as a rule betwi'en a pair of 

 the outward transverse branches of the lateral line. 

 To this he appends the remark that the presence of 



Fig. 309. Hyi>ia ainpiill;!' and tljeir o|ioiiing ducts tcisc'tlier with tlie 



dorsal course of tlie Intend line in tlie left half of a Raja. 



.After Gabm.\n. 



true sensory bulbs (nerve-bulbs) with tlie hair cells 

 oceurring in the lateral line has not yet been demon- 

 strated in the nerve ends on the inner wall of the 

 ampulla', whence he infers that the ampullar should 

 be regarded as a secretory part of the system of the 



lateral line. Their cavity is tilled with an endolymph- 

 like, more or less coagulated mucus. 



The third kind of organs belonging to this system 

 the so-called .sensory vesicles of Savi', appear only in 

 the Electric Rays, and are situated in one or two series 

 on the snout of these fishes and around the anterior 

 part of tiicir electiic organs. They are homologous 

 with the cacal bottoms of the ampulbe, but are entirely 

 closed, and their inner surface is usuallv furnished with 

 three sen.sory spots, the middle sjjot l)eing the liir"est 

 and furnished with numerous hair cells. 



The fourth kind (fig. oOS, po) of the sense organs 

 now under consideration are the so-called pit organs' 

 (called by Fiutscii'' spalt-papiUen). These are present 

 in our common Kays, and are wart-like dermal growths, 

 open at the top and containing a spherical or some- 

 what more prolongated (bottle-shaped) cavity, which is 

 filled with sensory cells furnished with hair-like pro- 

 cesses and surrounded by su])porting cells. The pit 

 organs or sensory follicles lie scatteri'd in rows along 

 the inferior orbital margins, in the temjioral region, 

 and on each side of the median line of the body, be- 

 tween tliis anil the trtie lateral line. 



The iiuiervation (.)f the entire system of the lateral 

 line is supplied, according to Ewart, almost exclusively 

 from branches of the facial nerve' and from the late- 

 ralis. The supraorbital branch (fig. 308, 1 — 6) and the 

 rostral tinijiulhe (Ru) are supplied by the superficial 

 ophthalmic division of the facial, the suborbital branch 

 and the anterior part of the occipital, the orbital ani- 

 pullaj {oa), and the pit organs {po) at the orbits by the 

 buccal division of the facial, and the hyomandibular 

 branch (12 — lU) together with the hyoid ampulke {lijia) 

 and the mandibular branch {27) by the hyomandibular 

 division of the facial nerve. The lateral line proper, 

 as well as the posterior part of the occipital branch, 

 the transverse occipital canal {21), and the majority of 

 the pit organs {po), is innervated by the lateralis, one 

 of the main divisions of the vagus. 



As Feitsch has remarked, some obscurity still 

 obtains in the question of the physiological importance 

 of the entire system of the lateral line; and the division 



" Die Elektrischen Fisclie, II, p. 87. 



' Matteucoi and Savi, Traitd des phenomenes electrophysiologiqiies des unimaiid; Paris 1844. 



' Trans. Koy. Soc. Edinb., vol. XXXVII (1891 — 92), p. 101. 



•' Stzber. Akad. Wiss. Berl., VIII (1888), p. 291. 



* This nerve consequently consists in fishes, according to Ewakt, of liotli sensory and motor fibres. In tlic liigher vertebrates it is 

 motor ahme, the sensorial parts, according to Ewart, having disappeared. According to the older opinion, wliicli is no doubt still niaiiitained 

 by tlie majority of anatomists, the divisions enumerated above belong to the trigeminal group. 



