ALTERNATE GENERATIONS. 245 



where they unite in a circular tube around the 

 margin and connect also with the four tenta- 

 cles ; from the centre of the lower surface hangs 

 the proboscis, terminating in a mouth. Not- 

 withstanding the delicate structure of this little 

 being, it is exceedingly voracious. It places it- 

 self upon the surface of the animal on which 

 it feeds, and, if it have any hard parts, it simply 

 sucks the juices, dropping the dead carcass im- 

 mediately after ; but it swallows whole the little 

 Acalephs of other Species and other soft ani- 

 mals that come in its way.-- Early in summer 

 these Jelly-Fishes drop their eggs, little trans- 

 parent pear-shaped bodies, covered with vibratile 

 cilia. They swim about for a time, until they 

 have found a resting-place, where they attach 

 themselves, each one founding a Hydroid stock 

 of its own, which will in time produce a new 

 brood of Medusae. 



This series of facts, presented here in their 

 connection, had been observed separately before 

 their true relation was understood. Investigations 

 had been made on the Hydroid stock, described 

 as Coryne, and upon its Medusoid offspring, de- 

 scribed as Sarsia, named after the naturalist Sars, 

 whose beautiful papers upon this class of animals 

 have associated his name with it ; but the inves- 

 tigations by which all these facts have been asso- 

 ciated in one connected series are very recent. 



