MOUPflOLOGT OF BRAIN AND SENSE ORGANS OF LIMULUS. 15 



There are a few very large ganglion-cellsj with coarse^ 

 anastomosing, plasmodia-like processes, that run at pretty- 

 regular intervals one above the other around the inside of 

 the spines (fig. 1). One may often isolate great masses of this 

 finely fibrillate reticulum without finding a nucleus in it. It 

 usually overlies and unites large bundles of the slender stalks 

 of the gustatory cells, but the latter appear to pass through 

 the Plasmodium without change. 



The body of the gustatory cells resembles that of the 

 double retinal cells of Molluscs and Arthropods, described by 

 me in Area, Pecten, Acilius, Lycosa, and others, in 

 that the large nucleus is nearly always excentric, and a 

 spiral partition separates the cell into two more or less distinct 

 portions (fig. 12). In one lies the main nucleus, n} ] in the 

 other a small unstained body that I regard as the aborted 

 nucleus of the second cell, n^. The proximal end of the cell 

 is sometimes forked, each branch being continued into a 

 nerve-fibre. The interesting fact is thus established that 

 double cells are not confined to the retina. 



The cuticular canal of the gustatory organ can be readily 

 distinguished from other canals by the presence of a peculiar 

 swollen knee, or bend, near its outer third, the surrounding 

 cuticula of which stains more deeply in borax carmine than 

 elsewhere (fig. 1). Under favorable conditions one can see in 

 the "knee'' a kind of spiral thread, caused by what in some 

 cases appears to be a spiral ridge on the wall of the canal, in 

 others by a spiral nerve-like fibril that seems to surround more 

 or less loosely the chitinous tubule (fig. 13). A similar spiral 

 thread is sometimes seen on the isolated chitinous tubule 

 (fig. 6, a) ; when treated with dilute potash the tubule swells 

 a little, and a thin, finely granular layer is seen about it, 

 together with what appears to be an extremely delicate fibril, 

 wound spirally about the tubule and its sheath (fig. 14). 



In some of the cuticular canals there are a few slender 

 nerve-like cells loosely surrounding the chitinous tubule 

 (fig. 1) j in other cases these cells seem to be absent. That 

 the tubules of the gustatory organs and of the others described 



