On the Anatomy of Leptodora hyalina. By R. E. Forrest. 833 



In the ' Micrographic Dictionary,' the first part of the diagnosis 

 which speaks of the body being enclosed in the carapace is omitted, 

 but even in this revised form it will not admit Leptodora. 



I don't understand why Lilljeborg placed Leptodora in the 

 family Daphniadae, which is defined thus : " Superior antennae very 

 small, inferior large with two branches. Legs five or six pairs all 

 enclosed within the carapace." As the carapace of Leptodora is so 

 small that it does not completely cover one somite of the abdomen, 

 much less any part of the legs. 



The probable explanation is that Baird's arrangement was 

 founded only on those British Entomostraca with which he was ac- 

 quainted, and under these circumstances it will, I suggest, be best 

 to place Leptodora in a family by itself, and to modify the Cladocera 

 as defined in the ' Micrographic Dictionary,' by the alteration of 

 a single word. 



Order, Cladocera. Legs four to six pairs, generally branchial ; 

 eye single, and very large, antennae two pairs, inferior large, 

 branched, and adapted for swimming. 



Family I. Daphniadae ; Family II, Polyphemidte ; Family III. 

 Leptodoridas. Inferior antennae very large, two branched, both 

 four-jointed. Legs six pairs, none of them branchiform. Carapace 

 very small, not enclosing the body. Young passing through a 

 metamorphosis from the winter egg. 



VII. History. 



Leptodora hyalina was first discovered by Dr. Focke, who 

 found it in the moat of the city of Bremen in 1844, and exhibited 

 it at a meeting of the Natural History Society of that place. It 

 did not however receive any name until 1860, when it was described 

 in the ' Transactions ' of the Swedish Academy by Lilljeborg, who 

 had found it in the Swedish lakes. His treatise is written in 

 Swedish, but he gives a long Latin diagnosis. Miiller was the 

 first to find the male in the Lakes of Constance, Geneva, and 

 Denmark. Nicolaus Wagner discovered it in 1868 in Russia, in a 

 lake near Kasan, and not knowing that Lilljeborg had already 

 described and named it, he gave a description and four plates of it 

 under the name ot Eyalosoma dux. In 1873, Sars published some 

 notes on the development of the winter eggs. In 1874, Dr. August 

 Weismann published a very elaborate and careful paper on its 

 anatomy, with six plates, in the ' Zeitschrift fiir wissenschaftliehe 

 Zoologie,' vol. xxiv. Through the kindness of Mr. Crisp, I have 

 been able to examine this laper, which was translated for me by a 

 lady friend, and I find that there are one or two points on which my 

 observations do not agree with his. He draws all the setae on the 

 branches of the antennae equal in length, which in my view is not 



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