PISCES 185 



roots and the mixed nerves of the brain are not homologous 

 structures and may indeed coexist in the same segment. The 

 spinal dorsal roots, moreover, lie medial to the myotomes. On 

 the other hand, the cranial system of ganglia is carried back 

 as the lateral line system as it is forwards by the ophthalmic, 

 VII. As we have seen, this system is with the auditory an 

 intimately related system, the acustico-lateralis system of 

 special cutaneous sense organs. 



From such studies we see that, in addition to segmental 

 and primitive relationships, associations of function have taken 

 place longitudinally, and we can thus resolve the nerves and 

 their endings in the brain into groups : 



Sensory 



Somatic 



Special Cutaneous, I, II. 



Acustico-lateral, VII, VIII, X. 



General Cutaneous, V, IX, X, dorsal spinal. 

 Visceral 



Taste, VII, IX, X. 



General, VII, IX, X, dorsal spinal. 

 Motor 



Somatic, XII, ventral spinal. 



Visceral, III, IV, V, VI, VII, IX, X, XI. 



Sympathetic. 



Secretory. 



The urinogenital organs arise together in the coelomic 

 mesoderm, and the system is peculiar to the Craniata. 



The coelom is resolved into the dorsal segmented myocoel 

 and the ventral unsegmented splanchnocoel. They remain 

 connected for a period by narrow ducts which, like the 

 myotomes above, are segmental. From the third myotome 

 behind the head and extending backwards in succession this 

 connecting tube is the seat of formation of a primitive kidney 

 tube, and it has consequently been called the nephrotome 

 (%. 85). 



The upper part of the nephrotome is concerned in the 

 development of the sclerotome, and this is separated at the 

 time that the nephrotome loses its connexion with the myotome. 



