116 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



half of the body, being shorter even than in Thalia longicauda. The 

 aggregated Iasis zonaria, also, has the endostyle short and in the 

 anterior part of the body. In all three of these species there is a 

 considerable gap between the posterior end of the endostyle and the 

 intestine. In Pegea confederata the endostyle is short and in the 

 anterior part of the body, but the gap between the intestine and 

 endostyle, especially in the solitary form, is less marked. 



c 



Fig. 109.— Thalia democeatica, aggregated form, dorsal views of atrial siphons which have 

 been cut open on the mid-ventral line and the flaps laid out laterally: a, from a pacific 

 Ocean specimen; B, from a New England coast form; C, from a specimen collected off New- 

 port, Rhode Island; D, copied from Streiff (1908) 



The eyes of the aggregated Thalia democratica (figs. 110, 111, and 

 112) are very different from those of the other subgenera, but the 

 structural conditions and the development indicate the homologies. 

 Three distinct portions of the eye are seen on the antero-ventral 

 surface of the ganglion, an anterior, larger portion (ex), and two 

 somewhat asymetrical posterior portions {e'l and e'2). The 



