29 



components of the cranial nerves, which are to be distinguished 

 from each other by their si?,e and histological characters, by 

 their central origin or connections, and by their ultinate 

 distribution. Kingsbury ('97) made a careful extension of these 

 findings to several ganoids and teleosts; while Herrick ('97, 

 '9B, '99) has traced the conditions in the bony fish k/enidia 

 with adniirable clearness. Certain conclusions reached by Johns- 

 ton ('93b) from his study of the ganoid brain stand apart from 

 the general trend of recent work, and to these we shall return 

 further on. 



The principles developed by the researches of Strong, 

 Kingsbury, and Herrick, may now be applied to the cranial nerves 

 of Vustelus. There are to be distinguished five systems of 

 nerve components: 



a. The Somatic Vctor System. — This system of neurones 

 is homologous with the ventral-cornu neurones of the spinal 

 cord. The fibres take origin from cells having a ventral loca- 

 tion in the brain, and they innervate striated somatic muscles. 

 The only representatives of this class are the nerves of the 

 eye-muscles, the 111, IV, and VT, respectively. 



b. The General Cutaneous System is so called because con- 

 cerned with the innervation of the skin of the head, but it is 

 not associated with specialised peripheral sense-organs of any 

 kind. Its fibres are components of the V, IX, and X nerves, 

 and they are homologous with the somatic sensory spinal fibres. 

 The cell-bodies of these neurones lie ir sensory ganglia, and 



