LATEEAL LINE. 



79 



In Elasmobranchs four kinds of organs are included under 

 this head : (1) the lateral line proper, or mucous canals , with its 

 cephaHc ramifications ; (2) the ampullary canals, or Lorenzini's 

 ampullae ; (3) Savins vesicles ; (4) pit organs. The essential 



r'. 



CSO sot orn. 



opr Th Th Gp ! y^^, 7 



Fla. 41.— Diagram illustrating the distribution of the dorsal branches of the cranial nerves 

 and of the lateral line canals, and the position of the groups of ampullae in an Elasmobranch 

 (:ifter Ewart, from Gegenbaur). A auditory nerve with labyrinth ; it also points to the 

 groups of Lorenzini's ampullae ; Bu buccal branch of facial ; bu inner branch to part of 

 infraorbital canal, and to the inner buccal group of ampullae, bu' its outer branch which 

 supplies part of the infraorbital canal, and the outer buccal group of ampullae ; ch post- 

 branchial branch of facial to mucous membrane, and giving off motor branches to some 

 jaw muscles ; CSO, CSO supraorbital canal ; CJO, CJO infraorbital canal ; Fa, Fa' 

 roots of facial nerve ; Gp glossopharyngeal, arising under cover of the lateralis branch of 

 the vagus nerve ; Bm hyomandibular canal arising from the infraorbital, and giving off 

 the mandibular canal, the mandibular group of ampullae is in the angle between these two ; 

 Hm' branch of the hyomandibular nerve to the hyoid group of ampullae ; in intestinal 

 branch of vagus with ganglion, where it separates from fourth branchial branch ; In lateralis 

 branch of vagus nerve ; m mouth ; N nasal sac ; om deep branch of oculomotor giving off 

 short root of ciliary ganglion (shown, but not marked), the long root is also shown, as 

 are the short ciliary nerves to the eye ; opr root of ophthalmicus profundus ; opv dorsal 

 branch of same, giving off long ciliary nerves ; pol second branch of lateralis supplying some 

 lateral line sense organs and a row of pit organs, the first branch supplies the commissure 

 connecting the two lateral canals, and some sense organs of the main canal ; sof ophthalmicus 

 superflcialis facialis, which supplies the supraorbital canal, and the superficial ophthalmic 

 group of ampullae ; sot ophthalmicus superficialis trigemini ; it arises from the gasserian 

 ganglion ; sp spiracle ; Tr trigeminus ; F', V^, V^ the first three branchial branches of 

 the vagus nerve, each with a ganglion and with pharyngeal, prebranchial and post-branchial 

 branches ; F* the united fourth branchial branch of vagus and intestinal branch ; 1-5 

 gill-slits. 



part of these organs seems in all cases to be sensory patches 

 of the epidermis, consistmg of sensory cells, bearing short 

 sensory hairs, and of supporting cells. 



Neue Untersvichungen zur Anatomie der Seitenorgane der Fische, Arch 

 f. mic. Anat., 1879-80. Allis, Anatomy and Development of Lateral 

 Line system in Amia, Journ. Morphology, 2, 1889. Fritsch, Die electrischen 

 Fische, Leipzig, 1890. Ewart, Tlie sensory canals of Laemargus, Trans. 

 Roy. Soc. Edinburgh, 37, p. 59, 1891 ; and The sensory canals of the 

 skate, Ibid. Pollard, The lateral line system in Siluroids, Zool. Jahrb. 

 5, 1892. Cole, On tlie cranial nerves and lateral sense organs of fishes, 

 Trans. Linnean Soc, 1898. 



