1 66 Journal of Comparative Neurology. 



respecting the branchial sense organs, which appear later. The 

 mesoderm, therefore, has its source in the ectoderm in the 

 region of the central nervous system, and in other places. The 

 formation of the cranial nerves begins, according to Gorono- 

 witsch, "in the early stages of the mesencephalic curvature" 

 by differentiation from the mesoderm of the trunks of the mesh- 

 work [web] enveloping the nerve. The trigeminus is formed 

 only by the mesoderm, and has no relation to the derivatives of 

 the ganglionic outgrowths. In the formation of the supraor- 

 bital branch, however, the ectoderm of the supraorbital region 

 also takes part. The facialis, that is to say, the trunk of the 

 web enveloping the nerve, is equally composed of the out- 

 growths (the ganglionic one, secondare Leiste) and also of the 

 elements of the adjacent mesoderm. The glossopharyngeus, so 

 far as I am able to understand him, is formed by the participa- 

 tion of the second lateral metamer — the derivate of the third 

 outgrowth. In this way, the formation of the above-mentioned 

 nerves occurs in the region of the ganglionic outgrowths, though 

 not from them, but rather from the mesoderm which has been 

 derived from these outgrowths. It is evident that in this case 

 Goronowitsch simply gives an original explanation of facts al- 

 ready stated and, as he himself says, unites the opinions of 

 Gotte and His. How these opinions can be compatible is an- 

 other question. 



It seems to me that Goronowitsch has not sufficiently ex- 

 plained the exclusive participation of mesoderm in the forma- 

 tion of the nerves. It is also not clear how he presents the 

 origin of the nerve from the neuroblasts and the appearance of 

 the latter. If he defines the neuroblasts in the same sense as 

 His, he does not add anything new to the development of the 

 nerve; but if he admits the mesodermic origin of the ganglion 

 cells (independently of the outgrowths) it changes the composi- 

 tion of the cranial nerves essentially. 



The suffusion and loss of determinate contours in the 

 ganglion outgrowths is not necessarily an indication of the trans- 

 formation of their elements in the mesenchyme. In the Sela- 

 chians these outgrowths always preserve the character which 



