EYES AND NEURAL GLANDS IN CYCLOSALPA. 2OI 



The ordinary ganglionic cells form that portion next to the gan- 

 glion (Fig. 6, b\ A distinct though thin membrane then inter- 

 venes (Fig. 6, gs\ separating the small-celled portion from a 

 large-celled area (Fig. 6, I)'}, which extends to the wall of the 

 gland (Fig. 6, g"^'}, anc ^ ls separated from the gland by a thick 

 membrane (Fig. 6, hz). The thin membrane, which intervenes 

 between the small and large cells of the outgrowths is continuous 

 with the delicate membrane that surrounds the ganglion. . The 

 neural glands and their lateral ducts have walls made up of a 

 single layer of cells, except that the wall of that side of each 

 gland which lies next to the ganglionic outgrowth, is composed 

 of several layers of cells (Fig. 6, gu>\ These conditions are 

 very similar to those described for Cyclosalpa pinnata. 



SALPA PUNCTATA. 



The ganglion of the chain form of Salpa punctata (Fig. 12) 

 differs in shape from the nearly spherical ganglion of Cyclosalpa 

 dolichosoma-virgula. Its dorso-ventral axis is about one and one 

 half times the length of its anterior-posterior and transverse axes. 

 Twenty-seven nerves were counted (Fig. 2). As in Cyclosalpa 

 dolichosoma-virgula, they all arise from the equatorial zone of 

 the ganglion, with the exception of a single pair from the ventral 

 outgrowths. The average thickness of the peripheral cellular 

 layer (Fig. 12), is about one twelfth of the ganglion's mean 

 diameter. 



In a dorsal position, just beneath the ganglionic membrane, is 

 a double layer of rod-cells, with the thickened ends of the cells 

 of one layer abutting upon the thickened ends of those of the 

 other layer (Fig. 12, ex). These cells are not as elongated as the 

 rod-cells of the large eye, but their bulk is about the same and 

 their nuclei are about the same size. There are no scattered 

 groups of small rod-cells in the peripheral cellular layer of the 

 ganglion of Salpa punctata, such as have been described for Cyclo- 

 salpa dolichosoma-virgula. This group of rod-cells in the dorsal 

 part of the ganglion of Salpa punctata probably belongs to the 

 same category as the small eyes found in the ganglia of many 

 species. The presence of many sorts of these small groups of 

 rod-cells in different positions in different species renders homol- 

 ogies between them doubtful. 



