374 



GA.MMARHLE. 



As soon as they are placed in a tank the animals of 

 this species invariably dive to the bottom, and bury them- 

 selves beneath the stones ; but should a piece of cork 

 be placed upon the water, the animals will invariably 

 return and crowd the under surface of the float. 



But although they may like the surface of the water 

 their constant habitat is amongst the dark fuci which 

 grow with such fertility between the tide-marks. Their 

 habits are probably not so active as those of other 

 species, since we find that their natatory appendages are 

 often thickly covered with a species of Vaginicola, which 

 Mr. Tuffen West considers may probably be F. crystal- 

 Una. The following vignette illustrates this parasite. 

 It is figured by M. Rentsch* as a species of Gregarina 

 in his work on the Parasites of Gammarus ornatus. 



* Homoiogenesis. Erstes Heft. Gammarus ornatus und seine Schmarot- 

 zer. Wismar, 1860, 4to. 



