Dec, 191G] Profundus and Gasserian Ganglia in Plethodon 35 



(1) It forms a root which enters the medulla and during develop- 

 ment this root shows no signs of disintegration. (2) Although 

 the ganglionic mass is at every stage a syncytium in which 

 the cell boundaries are not easily discerned, there is no indication 

 of the breaking down of nuclear material at any stage. This, 

 if present, might indicate disintegration. The nuclear bound- 

 aries become, in fact, more definite from early to late stages. 



Summary of the Relations of the Profundus and 



Gasserian Ganglia From the 6 mm. Stage to 



THE 11.5 mm. Stage. 



A comparison of the flat reconstructions of the selected 

 stages of the development of the profundus and Gasserian 

 ganglia makes evident the following points: (Figs. 29, 30, 31, 

 and 32). 



(1) The anterior end of the profundus ganglion shifts from 

 early to late stages. It moves from a point at the anterior end 

 of the optic vesicle (Fig. 32) where it is in contact with the 

 lateral ectoderm to a position mesial to the optic vesicle at a 

 level half way between the optic stalks and the anterior end 

 of the vesicle (Fig. 29). In this position it has of course no 

 contact with the lateral ectoderm. 



(2) Roots appear in the 7 mm. stage (Fig. 30) as develop- 

 ment proceeds and there is a slight shifting ventrally of the 

 roots from the position in earlier stages. 



(3) There is a change in the shape of profundus from an 

 irregular oval mass over half as long as broad at its widest 

 point and tapering at both ends in early stages to an elongated 

 tongue-like projection, broad at the proximal and narrow at 

 the distal end in later stages. The level of the greatest dorso- 

 ventral breadth of profundus moves progressively posterior 

 with reference to the position of the proximal end of the Gas- 

 serian. (Fig. 29-32). 



(4) There is a change in the form of the ventro-lateral 

 projections of the Gasserian ganglion from younger to older 

 stages. It changes from a single large, rectangular projection 

 extending to the first visceral pouch to a comparatively slender 

 projection forked over the temporalis muscle. 



(5) There is an absence of the close relation with D. Lat. 

 Gang, on VII in the younger stages which is present in the 

 older stages. 



