450 THE AMERICAN NATURALIST [Vol. LV 



dangling egg-sacs within which the embryos undergo 

 complete development. 



During the last few years our knowledge of the Sal- 

 mincola has been increased largely through the efforts of 

 Wilson and the present writer. Wilson, in 1915,- pub- 

 lished a key to the various species of Salmincola found in 

 North America, while the present writer (1912-1919)' 

 has published a series of papers on the behavior, mor- 

 phology, life-history and economic importance of two of 

 these forms, namely Salmincola echrardsii (Olsson) 

 Wilson, which parasitizes the brook trout of our middle- 

 western and eastern states, and Salmincola falculata 

 Wilson, which is parasitic on salmon and trout of our 

 Pacific states. In speaking of the former species, Small- 

 wood, in a recent paper,* says: 



These parasites are widespread in the United States in tlie native 

 trout streams, and in Canada and Europe. The tirst scientific record 

 of this particular parasite is l),v Linmnis in 17(51. Tt s.cni^ -tvAu^e. 



The writer is at present engaged on other species of 

 Sahnincola which dwell on various salmon and trout of 

 the northwest section of the United States. From all 

 appearances the different stages in the life histories of 

 the various species of Salmincola seem to be more or less 

 similar and, therefore, will be briefly outlined. 



As already mentioned above, the young larval copepods 

 undergo development within the egg-sacs of the attached 

 females. When these larvae are mature, they rupture the 

 egg-sacs and escape into the water as minute, freely- 

 swimming organisms that closely resemble free-living 

 pelagic copepods. Although they measure about one 

 thirty-fifth of an inch in length, they are very active and 



2 Pro,: r. S. Nat. Mus., Vol. 47, pj). 565-729. 



3 Report Wis. rush. Com., 1911-12, pp. 12-22. Jour. An. Brh., Vol. 3, pp. 

 36-60. Bio!. Bull., Vol. 27, pp. 115-127. Biol. Bull.. Vol. 'M. pp. 407-419. 

 Puh. Pufjet Sound Biol. Sta., Vol. 2, pp. 7;{-77. Puh. Pu^tt Sound Biol. Sta., 

 Vol. 2, pp. 153-181. 



4AMER. Nat., Vol. 52, pp. 322-352. 



