442 O. LARSELL 



the limiting membrane of the brain. The Hmiting membrane in 

 this region is bulged forward to a considerable extent. Some of 

 the cells appear to have passed beyond this membrane, at least 

 they lie outside of it, but their processes extend into the brain 

 substance. Similar cells were found along the entire course of 

 the nerve between the entrance into the brain substance of the 

 central roots and the rostral end of the olfactory bulb. The 

 position of a few of these cells is indicated in figure 7. 



These cells strongly suggest migratory cells, such as have been 

 pointed out in the ventral roots of the spinal nerves of the turtle 

 embryo by Kuntz ('11 b) and of the pig embryo by Carpenter 

 and Main ('07). These writers conclude that the ceUs which 

 migrate from the cord into the ventral nerve roots have a part 

 in the formation of the sympathetic ganglia, together with migra- 

 tory cells from the dorsal root ganglia. Gaskell ('16) takes a 

 similar view. 



A condition similar to that illustrated in figure 2 was observed 

 in a kitten one day old, and was illustrated in the previous paper 

 (fig. 23) on the nervus terminalis in mammals. No comment 

 was offered at the time on th6 point now under consideration, 

 since the observation had not been repeated in more than one 

 preparation. Such a relationship of cells is present in all of the 

 turtle embryos which are far enough advanced in development 

 to show distinct differentiation of ganglionic cells. 



CONCLUSION 



The nervus terminalis of the turtle takes part in the formation 

 of a plexus on the nasal septum, comparable to that found in mam- 

 mals. In the turtle fibers from the trigeminal nerve form a more 

 important share of this plexus than has yet been demonstrated 

 to be the case in mammals. 



There is a pronounced resemblance of the cells of the gangli- 

 onic clusters of the nervus terminalis to the cells of the various 

 sympathetic ganglia. This resemblance is apparent not only in 

 size, but also in their structure and manner of distribution and 

 to some extent, so far as the developmental evidence goes, in their 

 apparent origin as migratory cells from the central nervous 

 system. 



