Studies on niniiiu- Ostrarods 155 



thoroughgoing study of the organs of copukitioii in the Cytheridae, one of the most difficult 

 problems presented by this group of animals. 



For more detailed information with regard to the progress of the study of the O s t r a- 

 c o d s' special classification, morphology, etc. I may refer the reader to the historical resumes 

 to be found in the succeeding part of this work in connection with the discussion of the various 

 units of the system. 



During this period the fundamental features of the natural system of the s t r a c o d s yawral system. 

 underwent the following development: 



W. Baird was the first to divide this group into families. In his above-mentioned work 

 1850a, ,,Natural History of the British Entomostraca" a rather 

 eminent work for its time, this author divides the Ostracod group into three families*: 



Family I. Cypridae with the genera Cypris and Candoim. 

 ,, TI. Cytheridae ,, ,, ,, Cythere and Cythereis. 



„ III. Cypridinadae ,, ,, genus Cypridina. 



The families are classified by this author directly into genera. 



J. D. Dana makes a further very important advance. In his monumental work on the 

 Crustacea brought home by the ,,U n i t e d States Exploring E x p e d i t i o n" of 

 1852, he divides the Ostracod s, called Cypridacea or Cyproidea, into two families, both 

 composed of two sub-families: 



Family I. Cypridae, comprising the sub-families Cyprinae and Cyfherinne. 



,, II. Halocypridae. ,, ,, ., Cypridininae and Halocyprinae. 



The last-named sub-family comprises the two interesting genera discovered by this 

 author, Halocypris and Conchoecia. The sub-families are divided in this work directly into 

 genera and species. This classification may be said to form the basis of the present system of 

 the Ostracod s. 



The classification employed by G. 0. Sars in his work on the Ostracod s of Norway, 

 1865, certainly follows that worked out by J. D. Dana, but is, however, noteworthy partly 

 on account of the far-reaching extention of the new groups by the establishment of a rather 

 large number of new genera, partly by the founding of some new main groups, based on forms 

 that were completely or almost completely unknown to former authors, partly too because 

 in this work the names nowadays adopted for the large main groups were used for the first time. 

 G. 0. Sars divides the Ostracods into four sections, comprising altogether six families: 



Sectio I. Podocopa comprising the families Cypridae and Cytheridae 



,, II. Myodocopa, „ ,, ,, Cypridinadae and Conchoeciadne 



III. Cladocopa. ,, ., family Po/ycopidae 



IV. Platycopa, ,, ,, ,, CylhereUidae. 



- In a schome on p. li of the same work, in wliich VV. Daird says that he wishes to „give a connectMl view 

 of the arrangement of the British Entomostraca which I propose to adopt" this author, curiously enough, maizes tlie 

 Ostracods comprise only one family, named Cyprididae. including all the five above-mentioned genera. This 

 last-mentioned division is also found in this author's work of 1850c. 



