\'. KuPFFEK, Cranial Nerves of Vertebrates. 261 



the one over the second gill pouch. At the end of the 

 embryonic period, and after the release of the larvae, this 

 process advances cephalad into the region of the trigeminus, 

 and also caudad in proportion as the hind gill pouches 

 successively arise. These ganglia thus exhibit regular 

 branchiomerism, and those arising in the region of the 

 trigeminus point to aborted anterior gill pouches. 



How the branchial nerves, passing along by the principal 

 ganglia and proceeding to the visceral arches, connect with 

 the epibranchial ganglia, I shall show later. 



In the kind gill cegion, from the fourth primary gill 

 pouch to the eighth, the development of the peripheral 

 nervous system shows a less complicated course. The border 

 (leiste) growing out from the dorsal brain-plate appears first 

 as a continuous one, connects with the dorsal border cells 

 of the mesoderm segments and sends a ventral extension 

 between brain and mesoderm: there thus arises from it only 

 the dorsal spinal nerve, the rudiment of branchial nerves 

 remains apart from the border. There nevertheless arise, as 

 already mentioned, in regular order from the epidermis, the 

 epibranchial ganglia corresponding to the gill pouches of this 

 region. 



So long as the rudiments of the nerves consist of con- 

 tinuous chains of cells, it is not difficult to follow their 

 course and establish the connections. But there comes a 

 stage where, connected with the cells, fibrillfe appear and 

 separate the cells, and with this difficulty ensues for the 

 investigation, so long as the fibrill^e are not united into 

 thicker cords. The latter has occurred after the release of 

 the embryo, so the investigation is prosecuted on a firmer 

 basis. One can then enumerate the roots in the different 

 regions, and follow the ramifications of the distal nerves. 

 The stage intervening between the first rudiment, consisting 

 of continuous rows, and the later first evident compact nerve 

 cords renders uncommonly difficult the determination of the 

 question whether the rudiments and ganglia proceeding 



