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 Medusz. 
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. 
