58 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
(3) the crop diverticula are simple and never exceed six pairs in number, 
(4) All three species are small, (5) have relatively smooth skin, and (6) 
at least two of them bear the eggs in clusters attached symmetrically in 
a double row to the under side of the body, the condition in the third 
species being unknown. 
In parasitica and elegans (1) there are three pairs of eyes derived 
respectively from the sensilla of somites 11, 11, and tv., (2) the genital 
pores are separated by two rings, the anterior two rings of somite XII, 
(3) the crop diverticula number seven pairs and are lobed, (4) the in- 
tegument is rough and bears papille, (5) the attachment of the egg 
heteroclita 
fusca elegans 
stagnalis \ concolor 
‘ yi 
elongata \ / complanata 
\ 
| Lea 
\ \ parasitica 
\ \ ie 
\ 
Nell 7 
Ficure D. Diagram indicating relationships of the species described. 
clusters to the body, when such attachment exists, is imperfect and the 
arrangement of the clusters irregular. 
The European species complanata and concolor are very closely 
related to elegans, complanata certainly, perhaps also concolor, being 
intermediate between it and parasitica. 
In view of the many points of similarity between parasitica and com- 
planata, there seems to me to be insufficient ground for placing them in 
distinct genera, as proposed by Blanchard. 
Allusion has already been made to the somewhat isolated position of 
heteroclita. In size and in the character of its integument, it resembles 
the stagnalis group, likewise in the number of its crop diverticula ; in 
regard to the lobed condition of its crop diverticula, it resembles the 
parasitica group. In the number of its eyes (three pairs), it likewise 
resembles the latter group, but the derivation of these apparently is from 
different somites (111.-v. in heteroclita, 11.-Iv. in parasitica and elegans.) 
As regards the position of the genital pores and the way the eggs are 
borne, it differs alike from both groups. 
