DIVISIONS OF THE HYDROZOA. 67 
from the polypite about its middle or near its base. Near the 
insertion of these tentacles the generative buds are produced 
at proper seasons. In ELudendrium (the branched pipe-coral- 
line) thé essential structure is much the same as in 7zéu/arza, 
but the hydrosoma is now truly compound, consisting of a 
number of non-retractile reddish polypites, united by a coeno- 
sarc, which is furnished with a horny polypary, the whole 
colony assuming a singularly close resemblance to a plant. In 
Cordylophora—the only fresh-water member of the order—we 
find also a branched composite hydrosoma carrying numerous 
polypites, and having the ccenosarc defended by a horny sheath 
(fig. 18, a, 6). In Coryomorpha, finally, we have a type of the 
Fig. 18.—a Fragment of Cordylophora lacustris, slightly enlarged ; 6 Fragment of 
the same, considerably enlarged, showing a polypite and three gonophores in 
different stages of growth; ¢ Portion of Syncoryne Sarsii, with medusiform 
zodids budding between the tentacles. 
Corynida, in which the hydrosoma consists of no more than a 
single polypite, and there is no polypary. It is about fom 
inches in length, and is fixed by filamentous roots to the bot- 
tom of the sea. It consists of a single whitish polypite, striped 
with pink, and terminating upwards in a pear-shaped head, 
furnished with two sets of tentacles, the shortest of which form a 
circlet round the mouth. When young, the body of the animal 
is enclosed in a thin membranous tube, which seems to be 
wholly without organic connection with the animal itself, and 
which is wanting in fully-grown specimens. 
As regards the generative process in the Corynzda, it may be 
as well to consider the general phenomena of reproduction as 
carried on by all the Hydroid zoophytes, the general characters 
