218 UTILIZATION OF MINUTE LIFE. 



cession of births is only observed in all its grandeur 

 under the Tropics. It has been remarked, also, 

 that the larger species of polypes produce fewer 

 young. 



The Hydra that live in the ditches and stagnant 

 ponds around London, Paris, etc., die in the winter ; 

 but before this their body is replete with eggs or 

 buds, which are dispersed in the water in the form 

 of minute granular bodies, to become new polypes 

 the ensuing spring. These fresh-water polypes are 

 interesting objects of study for the fresh-water 

 aquarium, and as they are of a certain size, they can 

 be easily observed by means of a common lens or 

 magnifying-glass. It is curious to see them seize 

 in their tentacles small worms, insects, etc., and 

 carry them into their semi-transparent gelatinous 

 body. 



The same may be said of the Flustra, which 

 belong to the higher class of Bryozoa, and form inte- 

 resting specimens for the salt-water aquarium. Many 

 varieties of them are found on the sea-weeds, shells, 

 rocks, etc., which they cover with a minute network 

 of cells. Each cell contains a polype-like animal, 

 and there are in some species many hundred cells 

 in one square inch of this network. Again, the 

 Sertularia and the beautiful Campanularia, or bell- 

 shaped polypes, are sought for to decorate the 

 aquarium ; whilst Sea Anemones, on account of the 



