STATE GEOLOGIST. 123 



Leptodora liyalina, Lilljeborg, 

 (Plate N. Figs. 6, 7), 



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

 America. 



See Bail, mid Lehenserscheimmg von Leptodora hijallna, Weis- 

 mann, 1874:; also, Oi)i en dimorph Udvikling samt Generationsvexel 

 Jios Leptodora, G. 0. Sars, 1873; also, Bklrag til Cladocerenes For- 

 plantningshistorie, P. E. Mueller. 



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

 produced from the winter eggs pass through a metamorphosis not 

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

 ler mentions the pathological condition induced by the plants of 

 the Saprolegnia. 



