324 Journal of Comparative Neurology. 



The foremost ventral spinal nerve is a short fibrillar cord, 

 with cells disposed in and on it, which springs from the 

 ventral aspect of the mid-brain close outwards from its 

 basal plate. It proceeds between the fore end of the 

 chorda and the aorta, and approaches a hollow epithelial 

 cord which serves to connect with each other, under the end 

 of the chorda, a pair of bodies rich in yolk and lying later- 

 ally. There can be not doubt but that these two bodies are 

 the head cavities which Dohrn(') describes and from which 

 he derives the eye-muscles. If, however, Dohrn made his 

 observation upon these, the median piece connecting them 

 would not be a ventral but a dorsal structure, because the 

 carotis lies beneath it; so I must call attention to the fact that 

 this connecting part has its location over the carotis, indeed, 

 but under the blind foremost terminal piece of the aorta. 

 Recently Dohrn, departing from his earlier view, states that 

 the middle connecting part originates, in fact, from the 

 median fusion of two entirely distinct myotomes;(-) with 

 which I cannot agree. I consider the two head cavities 

 under discussion, together with the cord uniting them, the 

 foremost part of the anterior endodermal pouch which in 

 this stage of development has even separated from the hind 

 part of the pouch. 



Peculiar as is the behavior of the nerve now in approach- 

 ing this connecting piece destined to atrophy, I nevertheless 

 believe it may be considered as the oculomotorius, since the 

 paired praechordal head cavities, made single by the connect- 

 ing piece, always participate in the formation of the eye- 

 muscles. 



I must for the present leave undetermined whether a cord 

 which springs dorsally from the mid-brain, between the roots 

 of the first and second principal ganglia of the trigeminus, 

 and behind the eye approaches the second epibranchial gan- 



1 XII Stuilie. Mitteil. aus d. Zool. Station zu Neapel, Bd. VIII, 1887, pp. 325, 



328, 330. 



2 XV .Studie. Mitteil. aus. d. Zool. Station zu Neapel, Bd. IX, p. 332, Anmerk. 



