vou 2, it. 2.] A TAX0N0MIC STUDY OP THE SALPIDAE METCALF. 125 



(pi. 14), even in the peculiar appearance of the enlarged tips of the 

 inner tubes. Protuberances of the test at the posterior angles of 

 the body are found in numerous species, and in many of these species 

 they contain tubes whose epithelial lining is continuous with the 

 mantle. 



The gut is a round coil which may be called a "nucleus," though 

 it is less densely compacted than in the Apsteinias and Salpas. 

 One can make out the course of the intestine without dissection. 



I have not had sufficient material to study the histology of the 

 neural organs and gland. Examination of total preparations shows 

 the eye to be of the usual horseshoe form. 



THETYS VAGINA, aggregated form. 



There are five body muscles (fig. 117), all narrowly interrupted 

 dorsally and extending laterally only to the sides of the body. The 

 ventral half of the body has no muscles of any sort. The fifth body 



Y.O,rb 



FlQ. 117.— THETYS VAGINA, AGGREGATED ZOOlD VIEWED FROM THE RIGHT SIDE, I NATURAL SIZE. 



(Drawn by Hoyt S. Hopkins.) 



muscle is divided on each side into an anterior and a posterior 

 branch, as in the aggregated forms of other species, but the posterior 

 branches are short and do not pass below the atrial siphon or give 

 rise to any visceral muscle. 



The intermediate muscle is as in the larger of my specimens of 

 the solitary form of this species, not being fused with the rudimen- 

 tary first sphincter of the upper lip. The oral musculature, includ- 

 ing the horizontal dorsal band, is like that of the solitary form, 

 except that there are three, instead of two, dorsal sphincters, the 

 first very short and very slender, the second also very short. The 

 musculature of the atrial siphon, also, is like that of the solitary 

 form, except that there are 12 to 15, instead of 11, sphincters in my 

 specimens. On the dorsal side the basal sphincter is widely inter- 

 rupted in the middle, and ventrally its euds do not come into contact 

 with the atrial retractor muscle. 



