studios on marinn Ostrarods 155 



thoroughgoing study of the organs of copulation in the Cyiheridae, 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 U 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 y antral sysiem. 

 underwent the following development: 



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

 1850a, ,,Natural History of the British E n t o m o s t r a c a" a rather 

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



Family I. Cypridae with the genera Cypris and Candona. 

 ,, IT. Cytheridae ,, ,, ,, Cythere and Cythereis. 



,, ni. Cypridmadae ,, ,, 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 E x p 1 o r i n g E x p e d i t i o n" of 

 1852, he divides the O s t r a c o d s, called Cypridacea or Cyproidea, into two families, both 

 composed of two sub-families: 



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



11. Halocypridae, „ „ „ Cypridininae and Halocyprinae. 



The last-named sub-family comprises tlie 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 O s t r a c o d s. 



The classification employed by G. 0. Sahs in his work on the s t r a c o d 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 imknown 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. SAliS divides the Ostracods into four sections, comprising altogether six families: 



Sectio T. Pndocopa comprising the families Cypridae and Cytheridae 



II. Mijodocopa. ,. .. .. Cypridinadae and Cunclioeciadae 



III. Cladocopa. „ ., family Polycopidae 



W. Flatycopu, „ „ „ Cytherellidac. 



* In a srhonu' on \>. 1 '■ of the sanio work, in wliiili W. H.Miin says tliat lie wislu-.s to ..^\\o a connected view 

 of the arrangomont of tlm Biitisli Enloninslrara wliicti I [iroposo to adopt" this aiitlior. cuiiously i-iionuli, maki's the 

 Oslrao ods comprise only one family, named Ciiprididne. ineUulinn all the five aluive-mentioneil irener.!. This 

 last-mentioned division is also found in this antlior's work of IS.IOr. 



