60G SUMMARY OF CURRENT RESEARCHES RELATING TO 



the visceral organs arise from cells which have their origin in the hind- 

 brain and in the vagus ganglia, and migrate peripherally along the paths 

 of the vagi. The phenomena observed in the embryos of turtle give 

 evidence in favour of the observer's view that the peripheral displacement 

 of cells taking part in the development of the sympathetic system is pro- 

 bably determined by the influence of hormones. In turtles as in higher 

 Vertebrates the cells which migrate peripherally from the cerebrospinal 

 nervous system into the sympathetic " Anlagen " have the same genetic 

 relationships as the cells which give rise to the neurones and to the neu- 

 roglia cells in the central nervous system. The sympathetic nervous 

 system is therefore homologous with the other functional divisions of 

 the peripheral nervous system, and the sympathetic neurones are homo- 

 logous with their afferent and efferent components. 



Sympathetic Nervous System in Fishes.*— A. Kuntz has made a 



study of the development of the sympathetic nervous system in Fishes. 



His researches are based on the embryos of three widely separated types, 



Acanthias vulgaris, Amia calva, and Opsanus tau. In all three the 



" Anlagen " of the sympathetic trunks arise as cell -aggregates at the 



median side of the spinal nerves. The cells which give rise to these 



" Anlagen " have their origin (a) in the spinal ganglia or the neural 



crest and (b) in the neural tube. These cells migrate peripherally along 



the paths of the sensory and motor roots of the spinal nerves. This 



agrees with the writer's findings in regard to the histogenesis of the 



sympathetic trunks in Mammals and Birds, but not with those of earlier 



investigators of the development of the nervous system of Fishes, except 



with those of Froriep. In embryos of Acanthias a large proportion of 



the cells which wander out from the neural crest and from the ventral 



part of the neural tube migrate peripherally before the spinal nerves 



have become distinctly fibrous. These cells become scattered in the 



mesenchyme, where they remain until they become aggregated to form 



the " Anlagen " of the sympathetic trunks. In embryos of Amia and 



Opsanus such precocious peripheral migration of nervous elements does 



not take place, but the cells which give rise to the rudiments of the 



sympathetic trunks migrate from the spinal ganglia and from the ventral 



part of the neural tube along the fibres of the dorsal and the ventral 



roots of the spinal nerves. This difference in the details in the course 



of the early development of the sympathetic trunks in these three 



widely separated types of Fishes is probably correlated with their habits 



of reproduction. It has probably arisen in response to the external 



conditions surrounding the embryos during the early stages of their 



development. The "Anlagen" of the sympathetic trunks gradually 



advance mesially from the spinal nerves until they lie at the dorsal 



surfaces of the cardinal veins. In the posterior region of the trunk in 



embryos of Amia and Opsanus the sympathetic "Anlagen" advance 



still farther mesially until they lie along the ventro-lateral aspects of 



the aorta. In this region the sympathetic ganglia send out cellular 



processes mesially, until the corresponding ganglia of the right and left 



sympathetic trunks are connected by bands of sympathetic cells encirling 



* Journ. Comp. Neur., xxi. (1911) pp. 177-214. 



