268 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
with the above, and concludes that the supposed differences arose from 
‘‘Vetat 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 XX VII, Fig. 10.) 
GENUS PODON and GENUS EVADNE. 
These are compact oval forms confined to the sea. See Claus, Zur 
Kenntniss des Baues der Polyphemiden, Vienna, 1877, for the best account 
of the anatomy. 
FAMILY LEPTODORIDE. 
Feet six pairs. Antenne with both rami four-jointed. Body 
elongated, not curved, shell very much reduced. 
*Leptodora hyalina Lilljeborg. 
PLATE XXXYV, FIGs. 6, 7. 
The only species, is found rarely in the larger lakes of Europe and 
America. 
See Bau wnd Lebenserscheinung von Leptodora hyalina, Weismann, 
1874; also, Om en dimorph Udvikling samt Generationsvexel hos Leptodora, 
G. O. Sars, 1873; also, Bidrag til Cladocerenes Forplantningshistorie, 
P. E. Mueller. 
The work of Sars is papaenaae valuable, showing that the young 
produced from the winter eggs pass through a metamorphosis not ex- 
perienced by the summer or parthenogenetic brood. P. E. Mueller 
mentions the pathological condition induced by the plants of the 
Saprolegnia. 
