308 PROCEEDINGS OF THE NATIONAL MUSEUM. tol. 39. 



reference to these parasites, and it proves to be one which is fully 

 substantiated by a careful study and comparison of the mouth-parts. 



Three or four years later Gerstaecker published (1881) that portion 

 of Bronn's Thierreich which includes the copepoda. Like his prede- 

 cessors, he also carefully reviewed and criticised the various systems 

 which had been proposed. But unlike them, he went a step farther 

 and made an earnest effort to combine the good points of all the 

 systems and eliminate as far as possible their errors. 



As a result he has given us a thoroughly revised classification, in 

 which we find the Ergasilidse placed among the tenants and half 

 parasites, between the Corycseidas and the Ascomyzontidse. But he 

 has included in the Ergasilida3 all the genera referred by other authors 

 to a separate family, the Lichomolgidse. These latter are only semi- 

 parasites, and hence Gerstaecker was obliged to place the Ergasilidee 

 where he did. It seems far better to separate these two families and 

 to include in the Ergasilidag only those forms which live on the gills 

 or the bodies of fish, and thus are as completely parasitic as the 

 Caligidse. 



Moreover, Gerstaecker has placed the Chondracanthidae among the 

 true parasites, at the very end next to the Lernaeopodidffi. And these 

 last two families are separated from all the others with no marks of 

 lineage to connect them, as though he were uncertain where they really 

 belonged. 



In 1892 Canu published a work entitled Les Cop^podes du 

 Boulonnais, in which he presents another revised classification of the 

 copepods, including both the free-swimming and parasitic forms. 

 He adopted the general arrangement of Thorell and Glaus, with certain 

 modifications. 



His first division was based upon the number of sexual openings in 

 the body of the female; those having but a single opening he called 

 Monoporodelphya, and they correspond exactly to the Gnathostomata 

 of Thorell and Glaus. All the rest of the copepods belong to the 

 group Diporodelphya, which is then divided into three subgroups. 

 Recognizing the fact that the Ergasilidae and their near relatives 

 really do possess mandibles and maxillae, he changed the name which 

 Thorell had given (Poecilostoma) and called the first of his subgroups 

 Monochila. It corresponds exactly to Thorell's Poecilostoma except 

 in name. 



In this same year (1892) Giesbrecht, including only pelagic forms, 

 based his first division upon the position of the movable articulation 

 between the fore and hind body, and the structure of the fifth thoracic 

 legs. His second divisions were made with reference to the structure 

 of the first antennas. 



In 1903 Prof. G. O. Sars published volume 4 of his great work on 

 the Crustacea of Norway. This dealt with the Copepoda Calanoida, 



