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



31 



of the eye in C. pinnata (fig. 15, this page). This recalls the condition 

 of the developing eye of C. pinnata during the early part of its rota- 

 tion (fig. 12, D, p. 25). The position of the eye and the undivided 

 condition of its posterior portion, also the less developed state of the 

 plug in the adult Cyclosalpa affinis, parallel features of the immature 

 eye of C. pinnata. Shall we interpret this as indicating that C. 

 affinis is more archaic than 0. pinnata, or as showing it already to 

 have begun those retrogressive changes which culminate in the 

 decided degeneration of the eye in the more modified species of Sal- 

 pidae? The approach in the condition of the intestine to that of the 

 true Salpae, a secondary feature, makes one inclined to interpret the 

 divergence in the eye as secondary, a slight degeneration, consisting 

 of an inhibition of some of the later phases of the development. On 

 the other hand, the more 

 regular character of the 

 muscles in the aggregated 

 Cyclosalpa affinis is doubtless 

 more archaic than the condi- 

 tion in C. pinnata. 1 The evi- 

 dence from the muscles and 

 that from the gut are there- 

 fore opposed. Our studies 

 have inclined us to give 

 weight to the latter and to in- 

 terpret the comparative anat- 

 omy of the eyes accordingly. 



The two pairs of smaller eyes in the ganglion of the aggregated 

 Cyclosalpa affinis are similar to those in the chain form of C. pinnata. 



Our figures and description of Cyclosalpa affinis are based upon 

 the study of two specimens of the solitary form, one from an unnamed 

 locality, the other from the Atlantic Ocean, off the mouth of Dela- 

 ware Bay, in latitude 38° 24' north and longitude 71° 17' west [U. S. 

 Bureau of Fisheries station 2717]; of three embryos 1 1 mm. and 14 mm. 

 long, from the Atlantic Ocean, south of the eastern end of Long 

 Island, in latitude 39° 42' north and longitude 71° 17' west [U. S. 

 Bureau of Fisheries station 2749]; and of many specimens of the 

 aggregated form from the Atlantic coast of North America, from 

 Cape Hatteras to Cape Cod, and from the Pacific Ocean, off the 

 California coast, the station not being more exactly stated. We 



1 I have not followed the development of the body muscles in embryos or buds of Cyclosalpa affinis or 

 Cyclosalpa pinnata. In the development of the aggregated zooids of Thalia democratica, one sees that 

 the body muscles arise first as regularly spaced hoops, and their dorsal approximation into two groups, 

 as seen in the adult, occurs late in the development. This confirms the opinion that regular hoop-like 

 arrangement of the body muscles is archaic. 



2621— Bull. 100, vol. 2—19 3 



Fig. 15.— Cyclosalpa affinis, aggregated zooid, a 

 cross section of tiie posterior portion of tee dor- 

 sal eye. x 150 diameters. from metcalf (1s93, c). 



