206 ALBERT KUNTZ 



migrate peripherally along the motor nerve roots. The several 

 other investigators cited above seem to favor the theory that 

 the sympathetic system is derived in part from cells which have 

 their origin in the cerebrospinal ganglia (or neural crest) and in 

 part from cells which have their origin in the ventral half of the 

 neural tube. This theory is supported also by the writer's ob- 

 servations on embryos of types of the several classes of verte- 

 brates as well as by the work of Abel ('12) on embryos of the chick 

 and the extensive work of Ganfini ('11-' 18) on embryos of various 

 types of vertebrates. 



Held ('09) and Marcus ('09) are among the most recent investi- 

 gators who still maintain that the sympathetic nervous system is 

 derived exclusively from the cerebrospinal ganglia or the neural 

 crest. From observations made on embryos of Elasmobranchii, 

 Held argued that the cells present in the motor roots of the 

 spinal nerves play no part in the development of the sympathetic 

 trunks because, in these embryos, the primordia of the sympa- 

 thetic ganglia lie in contact with the sensory and not with the 

 motor nerve roots and there are no cellular connections apparent 

 between the latter and the former. Furthermore, the motor 

 roots apparently contain fewer cells than the sensory roots. 



The writer's observations on embryos of Acanthias suggest 

 that Held's conclusions are based on observations made on em- 

 bryos which were somewhat too far advanced in their develop- 

 ment to reveal the true relationship of the primordia of the 

 sympathetic trunks to the motor roots of the spinal nerves. As 

 has frequently been observed, cells migrate from the ventral 

 part of the neural tube into the ventral roots of the spinal 

 nerves in great abundance in early elasmobranch embryos. In- 

 deed Balfour ('77) described the ventral nerve root in such em- 

 bryos as ''an elongate cellular structure with a wide attachment 

 to the spinal cord." In transverse sections of early embryos of 

 Acanthias stained by the iron-hematoxylin method it may be 

 observed, as the writer has shown in an earlier paper ('11), that 

 some of these cells, as they advance peripherally, become scat- 

 tered in the mesenchymal tissue along the dorsolateral aspects of 

 the aorta with other cells of neural crest origin and later become 



