482 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxviii. 



But the life history was so little known up to 1852 that one of the 

 developmental stages, the chalimus stage, was regarded as an entirely 

 distinct genus, and several species were described by various authors. 

 F. Miiller (1852) and Hesse (1877), however, explained the chalimus 

 correctly, and recently A. Scott (1901) has given a brief life history 

 of L&peophtheirus pectoralis, in which the chalimus was still further 

 explained. But Scott states plainly that he has not worked out the 

 changes which take place in the developing embryo, so that we are 

 still left with only a general knowledge of the metamorphoses and 

 without a single authentic life history. 



The work of American authors upon these genera is somewhat 

 superior both in quality and quantity to that upon the Argulida?. 



Thomas Say, in his account of the Crustacea of the United States, 

 published in the Journal of the Academy of Natural Sciences at Phila- 

 delphia in 1818, mentions two parasitic copepods, jPandarus sinuatus, 

 found on the dogfish, and another which he calls Binocuhis ccmdatus 

 on Callianassa, the latter being evidently a species of Caligus. Fol- 

 lowing him came an admirable monograph by Dana and Pickering 

 (1838) upon Caligus americanus (= C curtus), which was the best 

 account of a single species published up to that date and which 

 remained without a rival until Scott's memoir just mentioned (1901). 

 The subsequent American papers came at considerable intervals. 

 Dana published several, which were entirely systematic, from 1843 to 

 1856. Smith in 1874 recorded all the species found in Vine} r ard Sound 

 and adjacent waters, while Rathbun gave (1884) an annotated list of 

 the species found in American waters, and in 1887 described a new 

 species of Trebius from Vineyard Sound. And yet out of more than 

 100 species belonging to the genera here considered only 7 have been 

 reported from North America and 6 from the West Indies. It is 

 time, therefore, that the lists were thoroughly revised, for these 

 parasites are as common upon the fishes of our own coast as they are 

 in European waters. 



The following account is drawn from all the sources here mentioned 

 and many other published papers; from the records of the United 

 States Bureau of Fisheries; from manuscript notes by R. R. Gurley on 

 The Vermine and Crustacean Parasites of Fresh- Water Fishes; from 

 very valuable manuscript notes and drawings by Richard Rathbun, 

 J. H. Emerton, J. H. Blake, and S. I. Smith, all of which were kindly 

 turned over to the author by Mr. Rathbun; and last of all from the 

 author's own personal investigations extending over several years. 



ECOLOGY. 



Advancing from a study of the Argulidse to that of Caligus and its 

 associates the first thing to be noted, since it is the key to most of the 

 changes we meet, is the fact that the female of these species carries 



