18 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



tion of the tube degenerates, the funnel becoming entirely separated 

 from the ganglion. The funnel becomes the dorsal tubercle. The 

 central cells of the ganglion degenerate and their place is taken by a 

 feltwork of fibers, which in section has a punctate appearance. As the 



central cells are degen- 

 erating, the dorsal cells 

 of the ganglion are in- 

 creasing in number, and 

 some of them are push- 

 ing up to form a ridge, 

 in the shape of a horse- 

 shoe, in which later the 

 histological differentia- 

 tion occurs which gives 

 the adult condition of 

 the eye. The rudiment of 

 the eye is, from the first, 

 horseshoe-shaped and it 

 continues in this form 

 (fig. 6). 



But one other set of structures needs mention in this description — 

 the neural glands and the outgrowths from the ganglion which are 

 connected with them. Ventral to the ganglion, on the right and on 

 the left, is a flattened horizontal chamber opening to the atrium by 



Fig. 6.— Cyclosalpa pinnata, embryo, a transverse section or 



THE DEVELOPING GANGLION AND EYE. X 150 DIAMETERS. FROM 

 METCALF (1893, C). 



..— CYCLOSALPA PINNATA, AGGREGATED FOKM, PARASAGITTAL SECTIONS THROUGH TnE GANGLION 

 NEURAL GLAND, AND THE OUTGROWTHS PROM THE GANGLION; FROM A DEVELOPING ZOOID. X 130 DIAM- 

 ETERS. From Metcalf (1893, c). 



a long slender and much coiled duct (figs. 7 and S. See also fig. 71, 

 which shows the similar, though larger, disks and ducts in the aggre- 

 gated zooids of Salya maxima). The walls of the chamber and of its 

 duct consist throughout of a single layer of epithelial cells. These 

 are the structures which Dober (1912) and others have called otocysts. 

 I know of no indication of otocystic function (Metcalf, 1893, c and 



