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ZOOLOGICAL EXERCISES. 
There are five sub-classes : 
Hydroida. Polypites provided with an ad- 
herent disc, and prehensile tentacles, 
Siphonophora. Hydrosoma free and oceanic, 
consisting of several polypites connected by a 
contractile coenosare, the proximal end of 
which is usually furnished with nectocalyces, 
and is dilated into a somatocyst or pneumato- 
phore. 
Discophora. Hydrosoma oceanic, consisting of 
a single nectocalyx, from which one or more 
polypites are suspended. Reproductive organs 
on the sides of the polypite, or on the necto- 
calycine canals. 
Lucernarida. The base of the hydrosoma de- 
veloped into an umbrella, in the walls of 
which the reproductive organs are produced. 
Hydrocoralla, Polypites secreting a sclero- 
dermic corallum. Hydrosoma attached, rigid. 
ActrnozoA. Alimentary canal separated from the 
body cavity ; reproductive organs external. 
There are two sub-classes: 
Zoantharia. Tentacles usually simple, nume- 
rous, In multiples of five or six. 
Alcyonaria. Polypes with eight pinnately 
fringed tentacles ; mesenteries in some multi- 
ple of four. 
CTENOPHORA. Swimming by means of comb-like 
plates bearing cilia. 
Three species of sponges from New Zealand have been 
