CORYNIDA. 123 
age, they present a central stomach, with four.canals in the form of a 
cross, and four to eight tentacles with cirri. The Corynide compre- 
hends many genera ; among others the genera Coryne, Hydractinia, 
Lubularia, and Cordylophora, in studying which Van Beneden of 
Louvain discovered most interesting facts connected with the subject 
of alternate generation. 
The- Hydrozoa forming the Corynidz have the power of secreting 
a hollow tube of a horny nature, in which the fleshy body can move 
up and down, expanding its tentacles over the top. Others of them 
give forth buds, each of which takes the form of a polyp, and these, 
being permanent, give it a shrub-like or branched appearance ; it is 
now a compound polyp. The tube is branched, but the orifices from 
which the polyps expand never dilate into cups or cells. The Tubu- 
laria are plant-like and horny, rooted by fibres, tubular, and filled~ 
with a semi-fluid organic pulp ; polyps naked and fleshy, protruding 
from the extremity of every branchlet of the tube, and armed with 
one or two circles of smooth filiform tentacles; the reproductive 
bodies germinating from the base of the tentacles ; embryo medusi- 
form. ‘Some modern authors,” says Frédol, “assure us that the 
tree-like form of these polyps is a degraded and transitory form of 
the Medusze. The Medusa originates the polyp, the polyp becomes a 
Medusa.” L£udendrium rameum so perfectly resembles an old tree in 
miniature, deprived of its leaves, that it is difficult to believe it is 
not of a vegetable origin ; it is like a vigorous tree in miniature, in 
full flower, rising from the summit of a brown-spotted stem, with 
many branches and tufted shoots, terminating in so many hydra-like 
polyps of a beautiful yellow or brilliant red. £. ramosum, of a 
brownish colour and horny substance, rising six inches, is rooted by 
tortuous, wrinkled fibres, with flexible, smooth, and thread-like shoots, 
branching into a doubly pinnate form. In Zubularia indivisa the 
tubes are clustering ; its numerous stems are horny, yellow, and from 
six to twelve inches in height, about a line in diameter, and marked 
with unequal knots from space to space, like the stalk of the oat-straw 
with the joints cut off. Their lower extremity is tortuous, attaching 
themselves readily to shells and stones in deep water, flourishing in 
deep muddy bottoms, and upright as a flower, fixed by the tapering 
root-like terminations of their horny tube: a flowering animal, having, 
however, neither flower nor branch. At the summit of each stem a 
double scarlet corolla is developed of from five to thirty-five petals, 
in rows, the external one spreading, those in the interior rising in 
a tuft ; a little below, the ovarium appears, drooping, when ripe, 
like a bunch of orange-coloured grapes. After a time the petals 
