VOL. _. I'T. 



2.] A JAXONOMIO STUDY OF THE SALPIDAE METCALF. 135 



IM. 



i.m. 



Fig. 124.— Pegea confederata, aggregated form, oral mus- 

 culature OF THE RIGHT SIDE, SEEN FROM THE INSIDE. FROM 

 SPECIMENS COLLECTED IN PHILIPPINE WATERS. 



The gut in the aggregated zooids is similar to that in the solitary 

 form. It is more or less covered by the tine brown branches of the 

 intestinal gland. In the loop of the gut lies the well-developed green- 

 ish yellow testis. Sur- 

 rounding the viscera in 

 the post abdomen is a 

 large blood sinus from 

 which vessels or lacunae 

 pass into the visceral 

 mass, usually between 

 the testis and the gut. 

 The open ends of these 

 vessels in surface view 

 look like perforations 

 such as would be made 

 by a dissecting needle. 



The neural gland shows 

 the usual two disks, each 

 with a convoluted duct. 

 There are a pair of elon- 

 gated, large-celled outgrowths from the ganglion, one on each side. 

 The eyes (figs. 126 and 127) are of interest. The large dorsal eye 

 is in two parts, a posterior portion (e") with the pigment below the 

 rod-cells, and an anterior portion (V) with its pigment above the rod- 

 cells. The optic nerve runs between 

 the two, giving fibers to each portion. 

 The rod-cells are irregular in shape 

 with irregularly thickened walls; that 

 is, they are degenerate. 



Comparison with the eyes of any 

 other subgenus except Traustedtia, say 

 with those of Cyclosalpa pinnata (figs. 9, 

 p. 23, and 12, p. 25), shows that in Pegea 

 there has been no reversal of the dorsal 

 eye such as has occurred in other Sal- 



+ ; "jf^ VSz pidas. In Cyclosalpa pinnata the optic 



nerve leaves the ganglion, passes above 

 the basal portions of the eye («')> some 

 of the fibers going on to the middle of 

 the eye where they pass through the 

 arch of the horseshoe to reach the rod- 

 cells of the apical portion of the eye (e"), some fibers being given off 

 first to innervate the optic plug (>'") (see Metcalf, 1893, c. pi. 48). 

 In Pegea the optic plug is wanting. The crucial point is that the optic 

 nerve passes directly to the rod-cells of the anterior portion of the eye, 

 not up and over this part of the eye. In Cyclosalpa the basal portion 



JZ 



CUS.S 



a.sj 



Fig. 125.— Pegea confederata, aggre- 

 gated FORM, ATRIAL MUSCULATURE OF 

 THE RIGHT SIDE, VIEWED FROM WITHIN. 



