384 



ADAPTIVE VARIATIONS. 



other organisms such as Myxomycetes, Actinos- 

 pherium, Crustacea, and tadpoles have been made by 

 other observers,* but it is unnecessary to mention more 

 than a single experiment, one made by De Varigny f 

 upon a number of different species of marine animals. 

 Some Carcinus mcenas, Pagurus Prideauxii, Dromia 

 vulgaris, Anthea cereus, Sagartia parasitica, Portunus 

 puber, Doris tuber culata, Venus, Actinia mesembryan- 

 themum, and Holotliuria tubulosa were placed in an 

 aquarium supplied with a constant flow of water. This 

 water was gradually diluted more and more with fresh 

 water, with the following results : 



On the 38th day, when the experiment was ended, 

 there were still living all of the original eight Actinia 

 mesembryanthemum and one Carcinus moenas. De 

 Varigny suggests that the greater resistance of A. 

 mesembryanthemum is probably connected with the fact 

 that these organisms are attached to rocks near the sea 



*For literature vide Davenport's "Experimental Morphology," 

 p. 86. 

 tCentralb. f. Physiol., i. p. 566. 



