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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 seusillte of somites ii., iii., and iv., (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 papillae, (5) the attachment of the egg 



heteroclita 



elegans 



concolor 



complanata 

 parasitica 



Figure D. Diagram indicating relationships of tlie 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 (in. -v. in heteroclita, ii.-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. 



