350 C. JUDSON HERRICK , 



In half grown Amblystoma larvae the relations just described 

 are seen except for some secondary shifting of parts, notably the 

 ventral movement of a part of the somatic sensory column along 

 the lateral surface of the oblongata so that the VIII and spinal V 

 roots lie superficially and ventrally of the fasciculus solitarius 

 (see figs. 13, 14). 



The four fundamental columns of the oblongata are readily 

 identified in both larval and adult Amblystoma so far as the central 

 connections of the peripheral nerve roots are concerned. The 

 somatic motor column contains the nucleus and roots of the VI 

 cranial nerve, the fasciculus longitudinalis medialis and some other 

 correlation tracts. The visceral motor column includes the motor 

 nuclei and roots of the V, VII, IX and X nerves. Only the 

 special visceral motor nerves for the striated visceral muscles of 

 the jaws, hyoid and branchial arches are clearly differentiated; 

 the general visceral efferent (preganglionic) components of these 

 nerves for unstriated muscles and glands have not been identified, 

 a feature probably to be correlated with the feeble development 

 of the head part of the sympathetic system in urodeles (cf. Hoff- 

 mann '02). The visceral sensory system is represented in the 

 portio intermedia of the VII nerve and in the visceral sensory 

 components of the IX and X nerves. All of these fibers enter the 

 fasciculus solitarius (fasciculus communis of Osborn) and termi- 

 nate in synaptic relation with the neurones of the adjacent parts 

 of the stratum griseum. The somatic sensory system is repre- 

 sented by the general cutaneous fibers of the V nerve and by the 

 component of the X (and probably of the VTI nerve also) which 

 enters the spinal V root, also by the special sensory systems of the 

 VIII and the lateral line roots of the VII and X nerves. 



The components of the cranial nerves of Amblystoma and their 

 peripheral distribution have been fully described by Coghill 

 ('01, '02). Professor Coghill informs me that these descriptions 

 were based upon large larvae 12 cm. long with functional external 

 gills, controlled by the examination of the adult after metamor- 

 phosis. The roots of the cranial nerves of the younger larvae used 

 in the present study are so similar to those of Coghill's specimens 

 that a separate description will not be necessary. Norris ('13, 



