EXPLANATION OF PLATES. 



a, accessory mass of optic cells ; b, small cells of latero-ventral outgrowths from 

 ganglion ; b f , large cells of latero-ventral outgrowths from ganglion ; bl, blood sinus ; 

 d, duct of neural gland ; dp, dorsal pigment cells of large eye ; dr, dorsally-directed 

 rod-cells of large eye ; e fft ' , " accessory portion "of Cyclosalpa pinnata eye ; ec, out- 

 line of ectodermal chamber above the ganglion ; ex, dorsal group of rod-cells in 

 ganglion of Salpa runcinata-fusiforinis and Salpa piinctata ; in Fig. 17 it indicates 

 a group of optic ce\\f, in Thalia deinocratica-mucronata which may be homologous 

 with the cells marked ex in the Salpee (cf. Figs. 12 and 20, Plate III. ); ey, ey' , ey", 

 groups of rod-cells in peripheral cellular layer of ganglion of Cyclosalpa dolichosoina- 

 rirgiila ; ez, a group of optic cells in Thalia democratica-mucronaia which is appar- 

 ently homologous with one of the posterior limbs of the horseshoe-shaped eye of 

 the chain form of Cyclosalpa pinnata ; g, ganglion ; ,<,v, fibrous core of ganglion ; 

 ;':, membrane surrounding ganglion ; h, neural gland ; //:, membrane separating 

 gland wall from large cells of latero-ventral outgrowths ; i, dorsal intermediate cells 

 of large eye; i', ventral intermediate cells of large eye ; /, peripheral cellular layer 

 of ganglion ; lp, lateral pigment cells of large eye ; //, laterally-directed rod-cells 

 of large eye ; n, nerve ; nc, nerve cells ; o, opening of duct of neural gland into 

 the pharynx ; oc, optic chamber ; on, optic nerve ; o s, optic ectodermal sheath ; 

 oz, optic membrane covering eye ; / /// , pigment cells of "accessory portion" of 

 Cyclosalpa pinnata eye; pc, pigment curtain in Salpa pit nctctta eye; fr, postero- 

 dorsal protuberance on ganglion of Cyclosalpa dolichosoma-mrgula ; q, group of 

 spindle-shaped cells in mid-dorsal region of Cyclosalpa dolichosoma-mrgula eye ; q' ' , 

 group of cells posterior to pigment curtain in Salpa punctala eye ; r" f , group of 

 rod-cells in eye of Cyclosalpa chatnissonis ; sc, supra-neural ectodermal chamber of 

 Salpa punctala ; vl, ventro-lateral outgrowth; vp, ventral pigment cells of large eye ; 

 Tr, ventrally-directed rod-cells of large eye ; gw, thickened portion of gland wall ; 

 .r, nerve which arises from one of the ventro-lateral outgrowths ; v, outline of optic 

 chamber ; z, limiting membrane of optic chamber. 



EXPLANATION OF PLATE VII. 



FIG. I. Dorsal view of eye, ganglion and nerves of Cyclosalpa dolichosoina-iirgi/la 

 chain form, showing also neural glands and ducts. The pigment of the eye is repre- 

 sented by heavy stippling. The ends of the rod-cells when visible are indicated by 

 faintly stippled outlines. The outlines of some of the blood sinuses are indicated by 

 dotted lines. The extent of the optic chamber is indicated by a contour-line. 



FIG. 2. Dorsal view of the eye, ganglion, nerves, glands and ducts of Salpa punc- 

 tata. The pigment of the eye is represented by heavy stippling. The rod-cells in 

 the dorsal part of the ganglion are indicated by faintly stippled outlines. The rod- 

 cells of the posterior portion of the large eye lie below so thick a layer of nerve 

 fibers that their outlines do not show. 



FIG. 3. The eye, ganglion, nerves and gland of the chain form of Cyclosalpa pin- 

 nata seen from the right side. The heavy stippling indicates pigment. The faintly 

 stippled outlines indicate the contours of the rod-cells. The contour-line indicates 

 the extent of the optic chamber. (Copied from Metcalf. ) 



FIG. 4. Dorsal view of the same. (Copied from Metcalf.) 



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