26o Journal of Comparative Neurolo(;y. 



ganglion.(') A more complete series of stages has sub- 

 sequently convinced me of the incorrectness of this view. 



The first trigeminus ganglion lies before and over the 

 second, can always be distinguished from this and is con- 

 nected with the nerve-rudiments of the fore head. 



The epidermal swelling next behind gives rise to the 

 labyrinth vesicle and the lateral part of the yacialis ganglion, 

 as likewise homodynamous parts, a portion of its cells 

 also entering into the rudiment of the glossopharyngeus. 

 Vesicle and ganglion arise in close connection, so that in the 

 beginning of the invagination of the pit of the labyrinth, the 

 ganglion is situated within, like a large knob, on the wall of 

 the pit. It becomes further enlarged through proliferation of 

 the cells of the wall. The root of the pertaining branchial 

 nerve itself enters by way of addition, as well with the gan- 

 glion as with labyrinth vesicle, and stretches to one other part 

 in this structure, lengthening in a ventral part. The ganglion 

 acquires a median portion from the latter. 



The third epidermal swelling, which belongs to the vagus, 

 is more stmple than the two preceding. There proceeds from 

 it a rounded, simple lateral ganglion, which, however, by 

 means of the root of the pertaining branchial nerve connect- 

 ing with it, acquires a considerable medial part and thereby 

 becomes a principal ganglion. 



During the formation of this principal ganglion, and 

 before it has yet completely separated from the epidermis, 

 there appear new growths of the epidermis. They lead, in 

 like manner, to the formation of ganglia, without the 

 connection with them of rudiments of sense organs, at 

 least directly. These are the epibranchial ganglia (Figs. 

 4, 6, 7 ge). They arise singly, close above the three 

 primitive gill pouches, and lie thus in a second series 

 removed ventrally from that of the principal ganglia. The 

 epibranchial ganglion appearing first is not the formost, but 



t Arch. f. Mikr. Anat., Bd. 35, 1890, S. 538. 



