VOU2.pt. 2.] A TAX0N0MIC STUDY OF THE SALPIDAE METCALF. 99 



Apsteinia punctata. It consists of a single layer of rather snort but 

 well-developed rod cells, whose thick-walled ends ("rods") lie 



an. 



P — < 



^O.S. 



as. B c 



Fig. 88. — Salpa cylindrica, aggregated fobm, transverse vertical sections of the ganglion 

 and doesal eye: j, is near the base of the eye: c, near the tip; and b, intermedlvte. x 360 

 diameters. from metcalf (1893, c). 



external, just beneath the limiting membrane of the ganglion. The 

 thin-walled ends of these rod colls are innervated directly from the 

 large optic nerve which 

 passes between the ac- 

 cessory eye and the large 

 dorsal eye. 



Close relationship of 

 Salpa cylindrica to the 

 other true Salpae seems 

 to be indicated by the 

 close resemblance of their 

 solitary forms and by the 



11 • f A 



resemblance m lorm and © a » 



musculature between their fig. 89.— Salpa cylindeica, aggregated form, vertical 



aggregated zooids. The 



unique character of the 



eyes of the aggregated zooids is remarkable. They foreshadow, in 



some regards, the eyes of Thalia, as will be seen later. 



THE ACCESSORY EYE AND PART OF THE 



ganglion. From Metcalf (1S93, c). 



