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STATE GEOLOGIST. 123 



Leptodora hyalina, Lilljeborg, 

 (Plate N. Figs. 6, 7), 



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

 America. 



See Bail und Lebenserscheinung von Leptodora hyalina, Weis- 

 mann, 1874; also, Om en dimorph Udvikling samt Generatmisvexel 

 hos Leptodora, G. 0. Sars, 1873; also, Bidrag til Cladocerenes For- 

 plantningshistorie, P. E. Mueller. 



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

 produced from the winter egajs pass through a metamorphosis not 

 experienced by the summer or parthenogenetic brood. P. E. Muel- 

 ler mentions the pathological condition induced by the plants of 

 the Saprolegnia. 



