324 Anatomical Notes on Sutroa Alpestris. [zoe 



sperm-sacs begin in XIII and extend to somite XX or further. 

 Ovary in somite XXXIL Egg capsule globular and pointed. 



Testes in somite IX. 



Habitat: In springs on the north and east side of Donner Lake 

 in the Sierra Nevada, California, at an altitude of about 6,000 feet. 

 Adult in the end of July. 



This species lives in the mud close to the surface of the water, and 

 is often found crawling on the underside of pieces of wood among 

 the roots of moss or smaller plants, or even attached to stones 

 partly submerged in the water. The color of this species is much 

 less vivid and iridescent than that of Sutroa rostrata^ which latter 

 must be considered as one of the most beautiful of all fresh water 

 Oligochsetse. 



As to size, Sutroa rostrata is by far the larger, being thicker, 

 but not as long as Sutroa alpestris. In shape the body of Suifoa 

 rostrata is more quadrilateral than that of our new species, in this 

 respect very much resembling Rhynchelmis. 



I will now enter more fully into a description of the anatomical 

 characteristics of the new species. 



Vascular System — consists of two main vessels: the ventral 



vessel and the dorsal vessel. (Figures 24 to 29.) The ventral ves- 

 sel is not pulsating; the dorsal vessel is strongly pulsating; the blood 

 is reddish as in the other species of this family. The ventral vessel 

 is forked in somite V, and differs in this respect from the ventral 

 vessel in S, rostrata, which is forked in somite VIII. 



The two forks of the ventral vessel are connected wath the dorsal 

 vessel in every somite by one pair of secondary vessels (as seen in 

 Figs. 24 and 25). In this respect the species resembles Rhymchelmis 

 Itfnosella, but differs from S. rostrata, in which there are no such 

 secondary vessels connecting the ventral and dorsal vessels, but 

 oitly secondary vessels connecting the two forks of the ventral vessel. 



In Sutroa alpestris the two forks of the ventral vessel are not con- 

 nected. 



The dorsal pulsating vessel connects m every somite except in 

 the extreme caudal somite with the ventral vessel through secondary 

 perigastric vessels. In the six anterior somites there are but one 

 pair, or two perigastric vessels in each somite— one vessel on each 

 side of the dorsal vessel. In the posterior somites, beginning 

 with somite VII, are two pairs of perigastric vessels, one post- 



