vou 2, pt. 2.] A TAXONOMIC STUDY OF THE SALPIDAE METCALF. 



23 



of the posterior face of the ganglion (ey). These have no pigment. 

 The thin-walled ends of the rod cells lie outward in the eye and to- 

 ward the surface of the ganglion. The dorsal pair of minute eyes 

 lie one below the base of each limb of the horseshoe-shaped larger 

 eye, on the dorsal surface of the ganglion (ex). The rod ends of their 

 rod cells are turned toward the surface of the ganglion, immediately 

 below the pigment of the larger eye. No innervation has been found 

 for any of the small eyes within the ganglion of this or other species 

 of Salpidae. In some species pigment is found associated with them. 

 Projecting forward from the middle of the dorsal surface of the 

 ganglion is a large horseshoe-shaped eye nearly equal in bulk to the 

 whole ganglion (pi. 2, figs. 7-8). The middle of the curve of the 



pnep 



FIG. 9.— CYCLOSALPA PINNATA, AGGREGATED ZOOID, A PARASAGITTAL SECTION THROUGH THE GAN. 

 GLION, THE ACCESSORY EYES OF THE LEFT HALF OF THE GANGLION, AND THE LEFT LIMB OF THE 

 DORSAL EYE. THE FIGURE REPRESENTS THREE SECTIONS COMBINED. X 150 DIAMETERS. 



horseshoe and its two ends are thick; the sides are slender. Behind 

 and a little above the curved portion of the eye is a laterally elongated 

 plug of optic cells, lying above the space which intervenes between 

 the two limbs of the horseshoe. The figures show, without much 

 description, the structure of this large eye. Figure 8 (pi. 2) is a dorsal 

 view and figure 7 (pi. 2) a view from the right side of the eye and gan- 

 glion. Figure 9, above, shows a parasagittal section and indicates also 

 the position of the minute eyes in the ganglion. Figure 10, page 24, is 

 from a transverse section of the posterior limbs of the horseshoe. 

 Figure 1, page 11, is a diagrammatic drawing of one rod cell and a few 

 pigment cells. One readily sees in figure 9, above, the innervation of the 

 rod cells of the limbs of the horseshoe and of the plug, but no one has yet 

 shown for the adult the innervation of the rod cells in the arch of the 

 horseshoe. In the nearly mature eye, however, I have shown 1 nerve 

 fibers passing down between the limbs of the horseshoe to innervate 



i Metcalf, 1893, c. <•/., plate 48, figure 9, o. n". 



