632 A. A. W. HUBREOHT. 



as rudiments of organs which have phylogeuetically disappeared, 

 and which are only now retained in the ontogenetic develop- 

 ment ;" then (p. 43) "for the Gasserian ganglion there is no 

 indication of a connection with the epiderm;" and, lastly 

 (p. 52), " it appears to be hardly any longer possible to look 

 upon these nerve-ganglia (Nervenknoten) as simply homologous 

 with spinal ganglia." 



Baldwin Spencer ^ writes (loc. cit., p. 129) concerning 

 E,ana temporaria: "Along certain lines the cells of the 

 nervous layer proliferate, and it is by this proliferation that 

 the rudiments of the cranial nerves are laid down ;" further 

 (p. 130), "the development of the ganglia at the level of the 

 lateral line, and the fact of their long connection with the epi- 



blast at this point, is of great interest in connection 



with certain points in the development of the Elasmobranch 

 nerves." 



Concerning the developmental phenomena of the trunk- 

 region at this period, the spinal nerves are stated to be not 

 yet visible, " though the nervous sheath is clearly developed 

 and in this the lateral line." 



The author next mentions observations made by him on Dr. 

 Beard^s sections of Elasmobranch embryos, and goes on to say 

 (loc. cit., p. 131): 



" The Gasserian ganglion is, at all events in part, formed 



directly from the epiblast the same development 



takes place in the case of the ganglion of the third and 

 seventh nerve — in that of the ciliary ganglion the develop- 

 ment is particularly clear — The ganglia arise 



along a level of the lateral line continued on the 

 head." 



He next says : '' The curious origin of the ganglia of the 



cranial nerves points strongly to the conclusion that 



their present condition and nature must be regarded 



as a secondary and certainly not primitive condition. 



" In passing, I may just notice that on this supposition an 

 ' "Early Development of Ran a temporaria," 'Quart. Journ. Micr, 

 Sci./ Suppl., 1885. 



