610 



Systematica used the structure and jjosition of the mouth-parts as a 

 basis of classification. Latreille (1796) selected the fusion of the head 

 and thorax, together with the structure of the thoracic appendages, and 

 in his later editions does not even mention the mouth-parts. Lamarck 

 (1801) preferred the form of the gills, and the form and structure of 

 the thoracic appendages. Desmarest (1825) used the mouth-tube and 

 the number and structure of the thoracic aj)pendages. Burmeister 

 (1833) selected the antennae and the structure and arrangement of the 

 mouth-parts. H. Milne-Edwards (1840) united the parasitic Copepods 

 with the Pycnogonids and created out of the two a separate sub-class 

 (Des Crustacés suceurs) of the Crustacea. The former were then divided 

 according to the jointing of the thorax and the development of the 

 swimming legs, the second antennae, and the maxillipeds. Steenstrup 

 and Lütken (1861) made their division according to the kind of egg- 

 sacks and the arrangement of the eggs within them, thus shutting out 

 the male sex entirely. These two authors and Thorell (1861) were the 

 first to include parasitic forms along with the free-swimming species, 

 and to divide the entire group on a common basis. Thorell used for 

 this purpose the mouth-tube and mandibles, and the structure and 

 arrangement of the maxillae. Unfortunately he made a serious mistake 

 in denying the existence of mandibles in his second division, the Poecilo- 

 stoma. Claus corrected this mistake in 1862, adopting the first 

 (Gnathostoma) and third (Siphonostoma) of Thorell's divisions; he 

 then included the families which had been placed in the second under 

 the one or the other of them according to the structure of the mouth- 

 parts. 



Gerstaecker in Bronn's Tierreich (1881) adopted Claus' classi- 

 fication with a few minor changes. Canu in »Les Copépodes du Boulon- 

 nais« (1892) proposed the number of sexual openings in the female as a 

 primary basis of division, thus again excluding the male sex entirely. 

 Giesbrecht (1892), including only pelagic forms, separated them first 

 according to the articulation between the fore and hind body and the 

 structure of the fifth thoracic legs. His second division was based on 

 the structure of the first antennae. 



G. 0. Sars (1901 — 3) in his extensive work on the Crustacea of 

 Norway, divides the order Copepoda into seven suborders, each named 

 from the type genus which represents it, the Calanoida, Harpacticoida, 

 Oyclopoida, Notodelphyoida, Monstrilloida, Caligoida, and Lernaeoida. 

 No one thing is taken as the basis of this classification , but rather a 

 combination of all the differences which characterize these respective 

 types. For his division of these suborders he has adopted Giesbrecht's 

 basis of the structure of the first antennae in the Calanoida and uses 



