250 Journal of Comparative Neitrology. 



A. Froriep(') has pointed out the part played by the epi- 

 dermis in the development of the cranial nerves in mam- 

 malian embryos, where, in comparison with the condition 

 discovered by Van Wihje in Elasmobranchs, the share of the 

 epidermis in this process seems scarcely less important. In 

 cow embryos such processes take place in the region of the 

 facial, glosso-pharyngeal and vagus, whose course is briefly 

 as follows: In embrys 8-9 mm. long with three gill furrows 

 apparent outside and four pharyngeal pouches, the spindle- 

 shaped ganglion of the facial unites with a pit-like, sunken 

 and at the same time greatly thickened place in the epi- 

 dermis, which corresponds to the dorsal extremity of the first 

 external gill furrow. The same thing occurs with the glosso- 

 pharyngeus; here also the distal end of the ganglion in the 

 rudiment of this nerve unites with a greatly thickened and 

 depressed portion of the epidermis dorsad to the second 

 pharyngeal cleft. The vagus rudiment behaves similarly. 

 Its large ganglion locates itself adjacent to a thickened epi- 

 dermal surface, of the shape of a figure 8, which is situated 

 dorsad to the third gill furrow and the vicinity of the fourth. 



In cow embryos 15 mm. long the connections of the facial 

 and glosso-pharyngeus are lost, but not of the vagus, and 

 here the thickened mass of epidermis reaches deep into the 

 ganglion, so that the two components cannot be definitely 

 separated from each other. 



Froriep compares these " organs of the gill clefts," though 

 with reserve, to the connections, described by Van Wihje, 

 of the ventral branches of the same nerves with the epi- 

 dermis, dorsally to the gill clefts, and explains them as rudi- 

 ments of sense organs which do not attain further develop- 

 ment, and probably belong in the category of organs of the 

 lateral line but with which they cannot be fully homologous, 

 since the lateral organs of fishes are formed on the dorsal 

 branches of the cranial nerves. As those ganglia which enter 



1 " Rudiments af Sense-organs in the Facial, Glosso-pharyngeal and Vagus," Arch. 

 f. Anat. u. Physiol., Anat. Abth., 1885. 



