2^4 JoiKNAi. OK Com I'AKA ri\K Nki K01,0(;V. 



Judging from this, the entirely different position of the 

 neural cranial ganglia on the one hand, of the spinal ganglia 

 on the other, relative to the dorsal mesoderm, was not taken 

 into account by Beard in the comparison. 



In a lecently published article(') on the development of 

 Petromyzon Planeri, I have likewise treated of the method 

 of formation of the peripheral nervous system, in the course 

 of which the previous works of Scott and Shipley on the 

 same object received thorough consideration. 



On the one hand, my observations not only yielded a con- 

 firmation of the participation, discovered in Gnathostomata, 

 of the peripheral regions of the epidermis in the develop- 

 ment of the cranial nerves, but caused this participation to 

 appear still more considerable than could be admitted from 

 what was previously known. But, on the other hand, 

 facts emerged which do not accord with the results of the 

 above mentioned authors, and display the complicated nature 

 of the ci"anial nerves in a new light. 



I was then led to essentially the following conception of 

 the composition of the dorsal cranial nerves: Each one is 

 composed of two parts, a spinal and a lateral., which latter, 

 comprising all its components, can also be designated as 

 branchial. The first behaves, with respect to its origin, its 

 course and its relation to the dorsal mesoderm, entirely like 

 a dorsal spinal nerve of the trunk. The dorsal cranial nerves 

 thus originally contain parts homodynamous with the spinal 

 nerves, but thereto is added the second variously formed 

 component, which, arising with the spinal, proceeds over the 

 dorsal border of the mesoderm and is situated on the outer 

 side, between mesoderm and epidermis. It is these lateral 

 components of the cranial nerves into whose composition 

 growths of the epidermis enter, and that occurs in two series 

 lying the one above the other. I distinguished them as 

 lateral and epibranchial ganglia. The first lie in the hori- 



X "The Development of I'etromy/on I'laneri," Arch. f. Mik. Anat., Kd. 35, 1890. 



