384 



ADAPTIVE VAKIATIONS. 



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 Yarigny t 

 upon a number of different species of marine animals. 

 Some Carcinus mcenas, Pagurus Prideauxii, Dromia 

 vulgaris, Anthea cereus, Sagartia parasitica, Portunus 

 puber, Doris tuberculata, Venus, Actinia mesembryan- 

 themum, and HolotJiuria 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 mcenas. De 

 Yarigny suggests that the greater resistance of A. 

 mesenibryantJiemum 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. 



