EYES AND NEURAL GLANDS IN CYCLOSALPA. 199 



The large optic nerve, when it enters the eye, passes directly 

 above the thin-walled ends of the rod-cells in the posterior portion 

 of the eye (Fig. 5 ; Fig. 9, on}. The nerve can easily be traced 

 as far as the middle of the eye, but the course of the fibers be- 

 yond that point could not be satisfactorily determined. In sec- 

 tions through the tip of the eye, the nerve fibers seem to appear 

 ventral to the rod-cells (Fig. 5), and it seems probable that they 

 enter these cells at their thin-walled ends ; but the shrinking of 

 the protoplasm from the tips of the rod-cells, apparently due to 

 the action of the preserving fluids, makes the rod-cell walls more 

 clearly visible, so that it is very difficult to distinguish between 

 these cell boundaries and probable innervating fibers. Sufficient 

 evidence was not obtained to warrant a categoric denial of Gop- 

 pert's assertion that the rod-cells in the anterior portion of the eye, 

 in the chain forms, receive their fibers at their thick-walled ends, 

 though the indications are all against this belief. To conclu- 

 sively decide this disputed point of innervation, attempts were 

 made at macerating preserved material, but without success. 

 Any one able to obtain fresh specimens could probably determine 

 readily by maceration the manner of innervation. Best suited 

 for this purpose are the following species, in which the rod- 

 cells are well-developed : Cydosalpa pinnata, Cyclosalpa c/iainis- 

 sonis, Cyclosalpa dolichosma-virgula, Salpa runcinata-fusiformis, 

 Salpa africana-maxima, Salpa cylindrica, Thalia deinocratica-inn- 

 cronata, Salpa piinctata. 



The fourth kind of cells, found in the eye of the chain form 

 of Cyclosalpa dolichosoma-virgula, are those which have been 

 mentioned as perhaps peculiar to this species. They lie in a 

 single group, which is partially imbedded among the pigment 

 cells of the mid-dorsal region (Fig. 5, q\ Fig. 8, q ; enlarged, 

 Fig. 10, </). These cells are spindle-shaped, and have nuclei 

 about the size of the intermediate-cell nuclei. They are inclined 

 at an angle of about 45 to the long axis of the eye (Fig. 10), 

 and they are separated from the posterior rod-cells by the optic 

 nerve fibers. The anteriormost cells of the group are wholly 

 surrounded by pigment (Fig. 8, q}. There seems to be some in- 

 dication that these spindle-shaped cells receive at their posterior 

 ends innervating fibers from the optic nerve. A probable homol- 



