210 POPULAR HISTORY OF THE AQUARIUM. 



terminating in sucker-cups, by means of which this parasite 

 fixes itself upon its prey. It is not however immovably at- 

 tached to the fish upon which it lives, for it can detach itself 

 for a time and swim freely in the water, indulging in merry 

 gambols, one of its movements consisting in turning over 

 and over. One observer says that " he has seen an indi- 

 vidual turn over a hundred times in a minute, and that it 

 swam afterwards with such velocity, sometimes skimming 

 the surface, at others plunging deeper in the water, that he 

 could scarcely follow his motions with its eye." 



We have now however dwelt long enough on a class 

 which, however interesting, must not be permitted to en- 

 croach upon space which can hardly be spared from the 

 more peculiar objects of Aquarian study. 



