vol. 2, pt. 2.] A TAXONOMIC STUDY OF THE SALPIDAE METCALP. 



77 



n.s. 1-7 



is so greatly reduced (e'" , figs. 19 and 20, p. 48), is entirely wanting 

 in Apsteinia punctata. At the place where it should lie is an 

 intruding branch of the pigment layer (fig. 57, p. 78), which 

 is probably a reminiscence of the 

 former presence of the plug. The 

 other features of the large eye are 

 much as in Cyclosalpa virgula, except 

 that it is much shorter, more like the 

 eye of the aggregated Salpa maxima. 

 No pairs of minute eyes are found 

 in the ganglion. In the less aber- 

 rant Cyclosalpas there are two pairs 

 of those very small eyes. In G. virgula 

 there are a varying number of still 

 more minute groups of less developed 

 rod -cells. In Apsteinia punctata, 

 while the minute eyes are wanting, 

 there is a large group of rod-cells (ex) 

 in two layers, one above the other, 

 on the dorsal side of the ganglion, 

 just in front of the origin of the optic nerve. Similar masses of 

 rod-cells, in a corresponding position, are found in the aggregated 



Fig. 55.— Apsteinia punctata, aggregated 

 zooid, atrial musculature of the left 

 side, seen from within. from stred7f 



(1908). 



Fig. 56.— Apsteinia punctata, aggregated zoOid, dorsal view of ganglion, eyes and neural 

 glands. From Metcalf and Johnson (1905). 



zooids of other species of the subgenus Salpa (fig. 79, p. 92). In 

 S. cylindrica (figs. 87, p. 98, and 89, p. 99) the rod-cells form a single 

 layer; in S . fusiformis and S. maxima they are irregularly arranged 

 and degenerate. Homologous groups of rod-cells will be described 

 later for Thalia. 1 



The neural glands show the usual character. 



i And for Apsteinia asymmctrica, sec Appendix, page 183. 



