268 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 



with the above, and concludes that the supposed differences arose from 

 'Tetat de maceration des exemplaires examines." {Les Cladoceres des 

 Grands Lacs de la Suisse, p. 11.) This species may be looked for in the 

 depths of the Great Lakes. (See Plate XXVII, Fig. 10.) 



GENUS PODON and GENUS EYADNE. 



These are compact oval forms confined to the sea. See Claus, Zur 

 Kenntniss des Baues der FolypJiemiden, Vienna, 1877, for the best account 

 of the anatomy. 



FAMILY LEPTODORID^. 



Feet six pairs. Antennae with both rami four-jointed. Body 

 elongated, not curved, shell very much reduced. 



*Leptodora hyalina Lilljehorg. 

 Plate XXXV, Figs. 6, 7. 



The only species, is found rarely in the larger lakes of Europe and 

 America. 



See Ban und LebenserscJieinung von Leptodora hyalina, "VVeismann, 

 1874; also. Omen diynorph TJdvikling samt Generatiomvexel hos Leptodora, 

 G. O. Sars, 1873; also, Bidrag til Cladocerenes Forplantningshistorie, 

 P. E. Mueller. 



The work of Sars is particularly valuable, showing that the young 

 produced from the winter eggs pass through a metamorphosis not ex- 

 perienced by the summer or partlienogenetic brood. P. E. Mueller 

 mentions the pathological condition induced by the plants of the 

 Saprolegnia. 



