28 University of California Puhlications in Zoology. [Vol.8 



Genus Sagitta 

 Sagitta enflata Grass! 



PI. 1, fig. 1; pi. 3, fig. 14; pi. 4, fig. 26; pi. 5. fig. 39; pi. 7, fig. 45; 



pi. 8, fig. 47. 



Sagitta enflata Grassi (1883), p. 16; Strodtmann (1892), p. 18; 

 Beraneck (1895), p. 254; Aida (1897), p. 15; Doncaster 

 (1902a), p. 20; Krumbacli (1903), p. 632; Fowler (1906), p. 8. 



Sagitta fiaccida Conant (1896), p. 85. 



Sagitta gardineri Doncaster (1902b), p. 212. 



Sagitta brachycephala Moltschanofi' (1907). p. 208. 



Sagitta inflata, Ritter-Zahony (1908), p. 13; (1909b), p. 5. 



Sagitta furcata, Michael (1908), p. 68. 



General Appearance 



This species is the most transparent of all the Chaetoguatha. 

 When immersed in formalin and placed on a white background 

 the body is very indistinctly seen, appearing like a very thin 

 piece of slightly ground glass. The head and ovaries assume 

 a yellowish-cream color considerably more opaque than the rest 

 of the body. The tail is likewise more opaque, especially at the 

 tip, shading gradually into the transparency of the body. On 

 a black background (pi. 1, fig. 1) the head, intestine, ventral 

 ganglion, ovaries, seminal vesicles, and tip of tail assume a 

 whitish appearance contrasting markedly with the body which, 

 though nearly transparent, presents a slight tinge of grayish- 

 slate. From tip of tail the white gradually shades into the 

 black of the body. The outlines of the fins are barely visible. 



Characters 



Body tumid, retaining its form well. A distinct neck separates head 

 from body. Body much the widest at a point from 40 to 50 per cent 

 of total length from head. Lateral fields large. Muscles weak and thin, 

 being barely perceptible under a hand lens. Pronounced constriction at 

 tail-septum. Collarette absent. 



Anterior fin never extends to yentral ganglion. Distance from fin to 

 ganglion usually about 20 per cent, but varies from 17 to 26 per cent. 

 Position of greatest width always behind center of fin, varying from 

 63 to 73 per cent of its own length. Triangular in form with apex 

 directed anteriorly. 



Posterior fin longer and broader than anterior fin. Never extends 

 caudally much more than half the distance from tail-septum to seminal 

 vesicles. Never less than 50 per cent of fin in front of tail-septum, 

 varying from 57 to 70 per cent. Position of greatest width almost uni- 

 formly opposite tail-septum. Interval from anterior to posterior fin 



