64:2 EADIATA. 
general mode of reproduction is by a process of budding or gemmation, by which a portion of 
the substance of the creature is pushed out and becomes a living Hydra. This takes place in 
summer ; during the winter they produce oviform granules, which remain like seeds in the water, 
until the return of spring causes them to develop a new race of polypes. 
The most wonderful part of the history of these creatures is still to be told. It appears to be 
well ascertained that they may be propagated by being cut in pieces, each piece becoming a 
complete living animal. Trembley says : " I have opened a polype on my hand, extended it, 
and cut the simple skin of which it is formed in every direction; I have reduced it to little 
pieces, and, in a manner, minced it. These little pieces of skin, both those which did and those 
which did not possess arms, became perfect polypes !" 
The Hydrse arc exceedingly voracious, and feed only on living animals. The larvse of insects, 
worms, and the minute crustaceous animals which swarm in all waters, constitute their food. 
Sometimes two polypes will seize upon the same worm, when a dispute of course ensues, which 
occasionally ends in a very singular manner. If the weaker of the two does not feel inclined to 
let slip a booty for which he has perhaps been waiting with extended tentacles for several days, it 
sometimes happens that each polype swallows the end which has fallen to his share, until at 
length the worm being all gone, the mouths of the pair come into actual contact. They now 
find themselves in a position of considerable difficulty, wliich is sometimes terminated by the 
breaking of the worm ; but if this does not take place, the larger or stronger of the two seizes 
upon his antagonist, and swallows him, worm and all. After a time the swallowed polype emerges 
from his living tomb ; the worm, however, is gone ! One of the most singular circumstances con- 
nected with the digestion of the Hydra — a digestion which is capable of dissolving creatures of far 
higher organization than itself — is, that the creature may actually be turned inside out without 
any derangement of its functions; the old inner surface now acts the part of a skin, while that 
which was the outer skin adapts itself without difficulty to the performance of the work of diges- 
tion ! 
THE SERTULARID^. 
These polypes all live in societies, each polype being inclosed in a sort of horny cup, supported 
on a branched polypidom of the same consist- 
ence. These polypidoms are among the most 
elegant productions of the sea, and their struc- 
ture and formation arc extremely curious. 
Their delicate arborescent forms are con- 
stantly to be seen attached to the sea-weeds 
left upon the beach by the retiring waves. 
Among the species are the beautiful Her- 
mNG-BoNE, Halecium halecinum ; the Sea- 
Fir, Sertularin ahietina ; the Sea-Hair, S. 
operculata ; the Fern Coralline, S.f.licula; 
the Bottle-brush Coralline, Thuiaria 
thuia ; the Feather Coralline, Plumu- 
laria jjennatula ; the Sea-Bristle, F. seta- 
cea, and many others — these being common 
on the Atlantic shores. 
THE TUBULARID^. 
This family of hydroid polypes are for the 
most part social animals, frequently possess- 
ing a polypidom, which, however, when pres- 
ent, is of much less firm consistence than the 
hornv framework of the Sertularidse. The 
polypes are never entirely retractile within 
their tubes; the upper extremity is enlarged into a clavate head, surrounded by a variable num- 
TUBTJLAEIA CORONATA. 
