tou2.pt. 2.] A TAX0N0MIC STUDY OF THE SALPIDAE METCALF. 7l 



ph.ep 



There are no accessory eyes in the ganglion proper in the aggre- 

 gated Ritteria hexagona, but there are a pair of outgrowths (ey in figs. 

 45 and 47), one on each side, near the dorsal surface of the ganglion, 

 which contain cells closely 

 resembling the degenerate 

 rod-cells in the eyes of many 

 species of Salpidae; as for 

 instance, Salpa fusiformis, 

 solitary, dorsal eye (fig. 76, 

 p. 91), S. fusiformis, aggre- 

 gated, accessory eye (fig. 79, 

 p. 92), Thetys vagina, aggre- 

 gated, dorsal and accessory Fig. 47.— Ritteria hexagona, aggregated zooid, oblique 



({' IIO v, 19fi^ nilH SECTION OF GANGLION SHOWING A BIT OF ONE OF THE NEURAL 



eyes Ulg. IIO, p. 1Z0;, ailCl GLAND3 („/.) AND THE TW0 lateral outgrowths (ey.) from 



Pegea confederata, (figs. 126 the ganglion with their cells developed as degenerate 



anr\ 197 n 1 3fi and 1°2 bod-cells, x 150 diameters. From Metcalf (1893, c). 



p. 143). No pigment is associated with these masses of degenerate 

 rod-cells in Ritteria hexagona. The position of these outgrowths, just 

 above the disks of the neural gland, suggests their homology with the 

 large-celled outgrowths in other species. 



The Ritterias show close similarity to one another in their mus- 

 cular system, which is of the Cyclosalpa type, except that the body 

 muscles are more numerous. In the character of the gut they are 

 intermediate between the Cyclosalpas and the other Salpidae. In the 

 asymmetry of the aggregated zooid (in the three species in which the 

 aggregated form is known) they resemble the Cyclosalpae asymmetri- 

 cales and the Apsteinias. In fact some degree of asymmetry is 

 observed in the aggregated zooids of most species of Salpidae. 



APSTEINIA, new subgenus. 



It includes the species punctata, asymmetrica, and magalhanica. 



The species punctata may be taken as the type of this subgenus, 

 for it is the best known of the three species. We have had material 

 of only Apsteinia punctata. 1 Other species have been studied by 

 Apstein (1894, b), Fowler (1896), Dober (1912), and Streiff (1908). 



This subgenus is characterized by the marked asymmetry of its 

 aggregated zooids, in which it agrees with the Ritterias, Brooksia, and 

 some Cyclosalpas, and by the compact condition of the gut, which, 

 in both solitary and aggregated forms of all species, forms a "nu- 

 cleus," as in the higher Salpidae. The Apteiniae differ from the 

 Salpae, sensu strictu, in having all the body muscles in the solitary 

 forms in the condition of complete hoops, as in Doliolum. 



1 After this paper was in press material of Apsteinia asymmetrica was obtained. Sec Appendix, page 183 



