No. I.] SPHYRANURA OSLERl. 3 1 



dorsal ; but the lateral break up and fuse with the others. All 

 are connected by commissures. 



We find that in Sphyranura the lateral and ventro-lateral 

 nerves converge to a single cord before entering the caudal 

 lamina. Where they unite there is a strong transverse com- 

 missure (see Fig. 7) ; but the strongest commissure is that 

 in the caudal lamina itself, between the united cords, from 

 which various branches are given off to the various parts of the 

 lamina. The two commissures mentioned are not the only ones, 

 for at least two further delicate connecting strands between the 

 lateral and ventro-lateral nerves were observed in the position 

 indicated in the diagram. From the anterior extremity of 

 each lateral ganglion there projects forwards a bundle of nerve- 

 fibres, interspersed with ganglion-cells; these give rise to a very 

 complex nerve-plexus in the upper lip, many of the fibres of 

 which may be seen to originate directly from the scattered 

 ganglion-cells. After a Sphyranura has been subjected to 

 pressure for some time the fibrillated contents of the ganglion- 

 cells and their processes may frequently be seen to ooze out 

 through those branches which come nearest the surface, into 

 the blisters formed by the raising of the investing membrane. 



The nerve-cells have as limits of measurement, 20 ^ and 

 42 ^ and their nuclei, 8 ^l and 11^. They are unipolar or 

 bipolar, multipolar ones not being common, having been 

 observed only at the ends of the commissures. The nucleus 

 possesses one or several irregular chromatin-nucleoli, and 

 is generally placed eccentrically. The contents of each 

 cell bear a strongly-marked fibrillated appearance. In the 

 case of unipolar cells these fibrillse, if they are such, are 

 seen, at the blunt end of the cell, to curve around concentrically 

 with the periphery of the cell, and in the case of bipolar cells 

 the fibrillae of one pole can be followed distinctly into the other. 

 Transections of one of the poles, shov/ these fibrillae as granules 

 of the tint which is that of the ganglion-cells generally, the 

 granules or points being circumscribed by a clear interfibrillar 

 substance. (Fig. ^ b.) 



The method of hardening with Flemming's fluid and stain- 

 ing with alum-cochineal gives these nerve-cells a peculiar color, 

 somewhat like chocolate-brown. This tint is also present in the 

 poles, but diminishes in intensity the farther the polar process 



