OEGAN OF TOUCH IN FISHES. 



325 



the Torpedo has a system of mucous organs in intimate connec- 



tion with nerves of sensation 

 Plagiostomes. The system 

 commences, in the Torpedo, 

 by groups of globular vesicles, 

 fig. 139, M, arranged sym- 

 metrically, outside the elec- 

 trical organs, from which 

 tubes are continued in parallel 

 bundles until they separate 

 themselves to perforate the 

 skin, and terminate by ori- 

 fices, some at the dorsal, some 

 at the ventral surface of the 

 head. A branch of the gang- 

 lionic part of the fifth expands 

 upon the ampulliform com- 

 mencement of each of the 

 exist in Sharks. 



but this is common to it with other 



215 



One of the follicular nervous organs of the Torpedo. 

 Magn. lxxvii. 



muciferous tubes. Similar organs 

 Hunter placed first in the series of specimens 

 of organs of touch in Fishes the snout of the Spotted Dog-fish 

 (Scyllium), ' to show the manner of the nerves ramifying, as also 

 their apparent termination in this part, each ultimate nerve 

 appearing to terminate in the bottom of a tube or duct, the sides 

 of which secrete and convey a thick mucus to the skin.' 1 

 Jacobson compares them to the whiskers in the Cat. Besides the 

 rostrum, these nervo-mucous organs are situated upon the sides 

 and under part of the head, and on the fore part of the trunk ; 

 they are crowded between the masseter, fig. 132, /, and the 

 branchial openings, ib. q, where they separate into two groups, 

 one diverging downward, forward, and backward, to beneath the 

 pectoral fin ; the other directed upward, forward, and backward, to 

 the occiput. 



§ 61. Organ of Touch in Hcematocrya. — In the Dermopteri, 

 the A?ir/uillidce, Siluroids, and a few other Fishes, with the in- 

 tegument wholly or in part scaleless, or with very minute and 

 delicate scales, lubricated with mucus, the whole or major part of 

 the external surface may be susceptible of impressions from the 

 surface of extraneous bodies coming in contact therewith. But 

 in the majority of the class the exercise of any faculty of touch 

 must be limited to the lips, to parts of certain fins, or to the 

 specially developed organs called ' barbules.' 



1 xx. vol. iii. p. 55, prep. no. 1395. 



