474 lU'niois St((te Laboratory of Xaturdl History. 



The principal features of the circulatory system of J/, asi/m- 

 metriciis and of that of P. palnstris having already been 

 described at length in this paper, it has seemed unnecessary 

 to tabulate the characters of this system for all three genera, 

 and, instead, a summary from Eisen's description of E. 

 frigidus ('81, p. 3) is subjoined. 



There is in E. frigidus but one pair of lateral vessels in 

 each of somites I-IX, and they are perigastric, connecting the 

 dorsal and ventral vessels, those of IX and X extending 

 posteriorly through several somites in connection with the 

 spermiducal organs. A considerable number of somites 

 following X contain only gastric vessels, of which there is 

 but one pair in each somite. Each of about thirty posterior 

 somites contains two pairs of perigastric vessels, which are 

 connected with the dorsal vessel and end blindly in the 

 ccelomic cavity, all being short, and all more or less imper- 

 fectly forked or branched. There are no gastric vessels in 

 these somites. 



An examination of the foregoing table shows that sperm- 

 reservoirs ("storage chambers") are present in all three, 

 genera. These are specially modified regions of the sperm- 

 diicts, which are found in no other members of the family. 

 Other characters common to the three genera, but not so 

 distinctive, are the simple setft^, the eversible penes, and the 

 great extent of the sperm-sacs. These four characters taken 

 together may be regarded as distinguishing the subfamily 

 Ecli.jjidriUna from other Lii))ibriciil.<i:t-. As the three included 

 genera contain but one species each, the definition of genera 

 and species is not attempted. 



7'J. frigidus is distinguished from the other two members 

 of the subfamily by the absence of a prostomium and by the 

 presence of (1) several pairs of nephridia anterior to the 

 reproductive organs, (2) paired nephridia posterior to XII, 

 (3) but one pair of lateral vessels in each somite — excepting 

 thirty or more posterior ones in which are two pairs of 

 perigastrics ending blindly in th(! cd'lomic cavity, (4) two 

 pairs of testes, (5) paired spermiducal pores onX, (6) paired 

 spermatliecie and spermathecal pores in IX, and (7) paired 



