NERVUS TERMINALIS: TURTLE 431 



but sections of embryos of approximately the same stage which 

 were stained by other methods, indicate that the clusters are 

 composed of ganglionic cells, which from their position no doubt 

 belong to the nervus terminalis. 



Some details of this plexus of the ophthalmic nerve are illus- 

 trated in figures 5 and 6. As shown in the figures, relatively 

 small strands of fibers meet at nodal points, from which the indi- 

 vidual fibers are redistributed to bundles diverging at various 

 angles. No ganglionic cells could be observed about these nodal 

 points at this early stage. In older stages, however, cell clusters 

 of various sizes are numerous at the points where the ophthalmic 

 nerve ramifies on the septum, and are found as far forward (figs. 

 3 and 7) as the most rostral part of the septum. It seems likely 

 that the more rostral of these cells correspond to clusters of sym- 

 pathetic cells described and figured by Willard ('15) in Anolis. 

 The observation of Rubaschin ( '03) of a 'ganglion olfactorii ner.vi 

 trigemini' on one of the branches of the ophthalmic nerve in the 

 chick appears also to be related. 



At various points the branches of the trigeminus and of the 

 terminalis become so intimately related that the two cannot be 

 told apart, and the smaller strands of the plexus which continue 

 from these points, appear to contain fibers from both nerves. As 

 shown in figure 7, which represents a reconstruction from nine 

 serial sections, from which the finer strands of the plexus are 

 omitted, the nervus terminalis anastomoses with one of the 

 larger branches of the ophthalmic nerve just dorsal to the vome- 

 ronasal nerve. At the point of anastomosis is a large ganglionic 

 cluster. The two nerves had the characteristic different appear- 

 ance, previously noted, proximal to their point of union, but their 



Fig. 4 Reconstruction of the septal plexus of the ophthalmic branch of the 

 trigeminal nerve of a turtle embryo of 8 mm. greatest length, prepared by the 

 Cajal method. The figure was reconstructed from sections 79 to 92 of the series. 

 The numerals indicate the sections from which the adjacent structures were 

 projected. For the sake of simplicity, section 79 is indicated by the numerals 1, 

 section 92 by 14, and intervening sections accordingly. X 80. 



Fig. 5 Portion of the plexus from section 81, at point marked 3* in the pre- 

 vious figure, to show details of structure. X 385. 



Fig. 6 Portion of the plexus from section 88 of the series, at point marked 

 5* in the reconstruction, to show detail. X 385. 



