The Brain of Diemydylus Viridescens 275 



ganglia of the 7th and 8th are distinct (Fig. 83, 84, 92), the 

 latter being more ventrad. In the adult, from the 7th a 

 branch extends to the gasserian ganglion (Fig. 3, 4), and 

 from the united ganglion a branch, said to be a part of the 7th, 

 extends through the cephalic part of the ear, and branches 

 are distributed to the sensory epithelium of the ear (Fig. 40). 

 The observations recorded seem to agree with Ayers' studies 

 (2). Strong (48) says that in amblystoma a branch of the 7th 

 which innervates the lateral line, disappears when the animal 

 adopts a terrestrial life. In diemyctylus, with the return to 

 aquatic life, in the adult male, pockets are formed at the side 

 of the head (Fig. 40, II) which receive branches of the 7th. 

 There has not been time to study the changes of the nerve in- 

 volved, but it is possible that here is a fruitful line of work 

 upon the post-embryonic changes in a nerve. 



Gasserian ganglion. In the adult two branches of the 5th 

 and a branch of the 7th can be traced into and through this 

 ganglion which lies within the skull and close to the endolym- 

 phatic sac (Fig. 3, 23, 39). In the larva the ganglion is deeply 

 lobed (Fig. 63), the two cephalic portions are connected with 

 branches of the 5th, the more caudal with the branch of the 

 7th. 



IX, X, XI, XII. (Fig. 5, 65). The ectal origins of these 

 nerves form a series each arising at a more ventral level than 

 the preceding. The 9th is associated with a sulcus at the 

 dorsal edge of the medulla, and the loth with a more 

 ventrally placed extension of cells, which according to 

 His (26) would represent another sulcus which has been 

 obscured by growth. This is clearly seen in the larva (Fig. 

 86). In the adult the nth is seen to be an offshoot from 

 a deep-lying bundle of fibers arising in 'the myel, part of 

 which pass to the nth and part extend further cephalad as the 

 solitary bundle (Fig. 43). The origin of the 12th is far ventrad 

 (Fig. 88). In the larva is an indication of a dorsal root (.t 

 in Fig. 65), such as is mentioned by Kingsley in amphiuma 

 (30) and Froriep (14) in an embrj^o ruminant. 



