599 



the internal origin and peripheral distribution of these parts. This is 

 a slow but exact method of settling the many mooted questions regard- 

 ing the homologies of the cranial nerves. The research was suggested 

 to the writer by Prof. Osborn who found the very indefinite know- 

 ledge of the homologies and peripheral distribution of the nerves limited 

 his investigations upon the internal structure of the Amphibian brain. 



The forms observed are Spelerpes ruber ^ DesmogiiatJms fusca, Tad- 

 poles of common Frogs, Chorophilus triseriatics (?) and Bufo lentigi- 

 nosus. The third and fourth species have been worked out most com- 

 pletely and are to be understood as referred to unless it is otherwise 

 specified. 



The method has been that of serial sections through the entire 

 heads of small Amphibians, in order to observe the finer anatomical 

 relations which elude gross dissection and to determine the precise 

 nature of the fibres of the various nerves. 



Although the investigation is not yet completed, I have thought 

 it best to communicate some of the results which have been obtained 

 thus far. 



1. The Oculo-Motor Group. 



A small sensory intracranial twig was observed to arise from the 

 IV. nerve. 



The fibres of the VI. can be traced through the Gasserian ganglion, 

 preserving their continuity, but cannot always be easily distinguished 

 beyond this from the Ophthalmicus trigemini, with which they are 

 merged. 



The Ciliary Ganglion. — Extirpation of the ciliary nerves 

 was followed by nearly complete degeneration of the ganglion, only a 

 few scattered cells on the III. remaining. In Desmognathus there ap- 

 pears to be no well defined ciliary ganglion — only scattered ganglion 

 cells. 



2. The Trigemiuus aucl Facial. 



Trigeminus. — The fibres of the Trigeminus are of varying sizes, 

 the majority being small but Avith a number of large fibres among them. 

 I find that while [a] some of the latter are motor, entering the muscles 

 supplied by the Trigeminus, [h] a number of the large fibres can be 

 followed out in all the main branches of the Trigeminus until they are 

 seen to have a cutaneous distribution. Although not traced out, there 

 can be little doubt but that the [a] motor fibres are from the Trige- 

 minal motor nucleus, forming the minor root of the V. which is here, 



