G. GENERAL NATURAL HISTORY AND ZOOLOGY. 335 



Sea. In the blind crawfish from the Mammoth Cave of 

 America, and the sightless JVejj/irops of Formosa, the organs 

 of vision are reduced to the smallest condition consistent 

 with their retention ; and in the Cirripedes the eyes are rep- 

 resented by their nervous apparatus only. No JVcnq)lhcs 

 form occurred. Mr. Bate believes that he has demonstrated 

 that the three pairs of motile appendages in the Nauplius 

 form of larva homologize with the eyes and two pairs of an- 

 tennae, and not with the antenna? and mandibles, as stated by 

 Fritz Muller, Dohrn, and others. A^mals and Magazine of 

 JVatural History^ August. 



INFLUENCES OF EXTERNAL AGENCIES IN AETEMIA. 



Schmankiewitsch announces an interestinsc fact in resrard to 

 the variation of animal species, in studying the Arteniia salina 

 from the salt marshes of Odessa a crustacean known from 

 its power of resisting the influence of concentrated brine. 

 At the beginning of his observations, owing to the rupture 

 of a dike, the quantity of salt in the ponds was quite small, 

 but after repairing the concentration proceeded very rapidly, 

 and Avhat began as a typical Artemia salina was gradually 

 modified from generation to generation, so that in a few years 

 the animal lost its caudal lobes, and then presented all the 

 specific characters of a second species, the Artemia mul- 

 Jiausenii. 



In an inverse experiment, or passing from a greater to a 

 less degree of concentration, the Arteniia niulhaiisenii was 

 made to return to the form of ^. salina. In further illustra- 

 tion of this subject, the author gives reasons for believing 

 that the entire genus Arteniia is only a degraded form of 

 Branchipus^ a fresh-water form, changed possibly by a trans- 

 fer to a saline medium. 18-4, January 9, 423. 



STRANGE ISOPOD PARASITES OF THE HERMIT CRAB. 



M. Hesse has described two singular parasites belonging 

 to the Isopod Crustacea, and which are related to the Idotae- 

 ans, but are strangely modified by their parasitic habits. In 

 one form {Pleurocrypta) the parasite lives under the carapace 

 of its host, while in the other (Athelgue) the dorsal surface is 

 applied interiorly on the abdomen of the crab, and its gills 

 are exposed on this part of its body, while the entire ani- 



