\. KrPKFKR, Cranial Xcrvvs of ^'ertehratcs. 2c;9 



described and drawn in my article. But I must here, on the 

 the basis of later investigations, make some additions and 

 corrections. 



The trigeminus swelling, appearing close behind the eye- 

 rudiment, forms a projection (Fig. 4,^'/) directed entad and 

 dorsad, and consisting of closely crowded cells, upon which, 

 although still continuous, may be noticed two prominences 

 lying the one behind and under the other. The root of the 

 branchial nerve grows toward this swelling, unites with it 

 by means of a tract of cells, and passes along, with another 

 tract close by, growing in a ventral direction. The growth 

 of these nerve- rudiments results partly from division of these 

 cells, partly through the invasion of new elements from the 

 dorsal brain-plate. At the point of junction of the root of 

 the branchial nerve with the swelling of epidermis, there 

 results a multiplication of the cells belonging to the nerve 

 whereby two heaps of cells, corresponding to the two promi- 

 nences on the swelling, arise, the elements of which are 

 inserted between the epidermis cells of the swelling, so that 

 later on they could not be distinguished according to their 

 origin. 



From this complex two ganglia are isolated successively 

 with simultaneous separation from the epidermis, each of 

 which consists of two parts, one epidermal and one arising 

 from the dorsal brain-plate, of which the first part has been 

 designated by me the lateral, the other as the medial ganglion 

 (Figs. 5 and 7,^^/, ^"w). But the two parts are gradually 

 merged into each other, so that finally no clear boundary 

 between them can be pointed out. It is thus necessary to 

 designate the whole body as one, and 1 propose the term 

 '•'■ principaV ganglion (Hauptganglion) for it. There belong 

 to the trigeminus two principal ganglia, formed in the 

 same way, the Jirst and the second. The two are honio- 

 dynanious. I correct herewith my earlier view that the first 

 trigeminus ganglion is exclusively of central origin, and has 

 the same value as the medial part of the second trigeminus 



