Oalk ry 
VIII. 
Centre- 
Cases 
A4-A6. 
Wall-case 
12 . 
11(3 GUIDE TO THE FOSSIL INVERTEBRATE ANIMALS. 
BRYOZOA OR BOT.YZOA. 
The fossil remains of the Biyozoa (moss-animals), or 
Polyzoa, as they are often called, a group of which the 
modem Sea-mats are familiar examples, are exhibited in 
three cases in the middle of the gallery, adjoining tlie 
Brachiopoda, with which tliey are by some supposed lo be 
allied. These specimens are all British, and form an adequate 
representation of these widely spread fossils. In Wall-case 
12 are placed a few foreign specimens of particular interest, 
as well as certain colonies too large to find room in the 
British series proper. 
Pig. G1. — Diagram of structure of a typical Bryozoan zooid, a.s seen 
iu a vertical cut down the middle, an, anus ; ap, aperture ; b.c, 
body-cavity ; c.p, communication pore ; d, diaphragm ; ect, ectocyst ; 
end, endocyst ; /, funiculi ; n, nerve-ganglion ; o, orifice ; ces, oeso- 
phagus; op, operculum; r.vi, retractor muscle; st, stomach; T, 
tentacles ; t.s, tentacle sheath. 
Though often mistaken by wanderers on the sea-shore for 
sea-weeds, the Bryozoa are really animals. They live in 
either fresh or salt water, mostly iu the latter, and with 
one exception {Loxosoma), always form colonies, which are 
generally fixed. A colony consists of a large number of 
individuals (or zooids), each of which is completely separated 
from the rest and enclosed in a double-walled sac. The 
digestive tube is U-shaped, the mouth and anus being placed 
close together. A band of tentacles occurs round the mouth 
in most forms (Ectoprocta), but in one group (Entoprocta) this 
surrounds both the mouth and the anus. These colonies 
