267 
HYDRiE, OR FRESH-WATER POLYPES. 
BY REV. W. HOUGHTON, M.A., F.L.S. 
P ROBABLY no animal in the world ever excited more 
interest amongst naturalists than the little hydrae of our 
ponds and ditches. The interest has now, as is natural, con- 
siderably abated ; further acquaintance has brought to light 
so many strange facts and anomalies in the animal kingdom 
since the days of Leeuwenhoek and Trembley, that we cease 
to wonder greatly at any new revelation of nature. Though 
familiarity never breeds contempt, but, on the contrary, stimu- 
lates the inquiring mind to further discoveries, the naturalist 
of the present century does not stand amazed, as of old, at the 
record of any well-ascertained fact in science, however anoma- 
lous it may appear. Fresh discoveries nowadays may perhaps 
lack the charm of novelty — at least of a kind equal to that of 
Trembley's account of the hydra, — but they may have a more 
important scientific bearing, inasmuch as increased knowledge 
and greater facilities for minute investigations have made us 
better able to appreciate their value in the grand scheme of 
nature. Still, it is almost impossible to exaggerate the im- 
portance of Trembley's discoveries as to the nature of those 
little jelly-like substances, so common in almost every pond 
and ditch. To the ancient naturalists of Greece and Rome the 
veritable hydra was entirely unknown. The term “ polypus ” 
was used by them to designate various species of cephalopo- 
dous molluscs. With coral they were partially acquainted, but 
they knew nothing of its real nature. Theophrastus considered 
coral to belong to the mineral kingdom ; Pliny seems to have 
thought it was a vegetable ; and we know that this substance, 
now ascertained to be of animal nature, was, even up to the 
middle of the last century, considered to belong to the vegetable 
kingdom. Marsigli, early in the eighteenth century, noticing 
the flower-shaped bodies in Alcyonium and Corallium on the 
shore of the Mediterranean, considered their vegetable nature 
placed beyond a doubt. It is to Peyssonnel, a learned physician 
of Marseilles — how much valuable zoological knowledge we 
VOL. v. — no, xx. u 
