24 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



the ventral thin-walled ends of the rod cells of the arch of the horseshoe. 

 There are no intermediate cells between the rods and the pigment cells 

 in the eyes of the aggregated Cyclosalpa pinnata. Such intermediate 

 cells are present in the eye of the solitary form. In the aggregated 

 zooids of C. pinnata, as in those of all other species whose eyes have 



Fig. 10.— Cyclosalpa pinnata, aggregated zooid, a transverse sec- 

 tion THROUGH THE GANGLION AND THE TWO POSTERIOR LIMBS OF THE 

 DORSAL EYE. X 150 DIAMETERS. FROM METCALF (1893, C). 



been studied, the pigment cells are superficial. In the solitary C. 

 pinnata they lie deeper among the cells of the optic ridge. 



Goppert (1892) has shown the presence of ovoid phaeosphaeres 



in the rod cells of the large eyes of the aggregated forms of Cyclosalpa 



pinnata and Pegea confederata, also in the eye of the solitary Salpa 



e maxima. I have not succeeded 



in demonstrating these, but 



doubtless careful work upon 



better preserved material would 



show them. One can not doubt 



the accuracy of Goppert's 



studies. 



The development of the 



large eye of the aggregated 



Cyclosalpa pinnata must also 



bc-lu, be described, as it is an im- 



Fig. 11.— Cyclosalpa pinnata, aggregated form, a portant aid to Understand- 



TRANSVERSE SECTION OF THE DEVELOPING EYE. THE Jjjg ^q taXOllOmic Value Of the 



TWO ANTERIOR LIMBS (e) OF THE AT THIS STAGE HORSE- . , , 



shoe-shaped eye are shown, x 200 diameters, comparative anatomy oi tne 

 from metcalf (1893, c). e y 0S f the aggregated forms 



of the several species of Salpidae. When first discernible the 

 rudiment of the eye is exactly similar to that in a young embryo 

 of the solitary Cyclosalpa pinnata, a horseshoe-shaped ridge of 

 cells, above the ganglion, with the ends of the horseshoe anterior 

 (fig. 11). The simplo horseshoe shape of the eye of the solitary 



ep... 



