36 
Tank No. 21. 
The graceful net-like frill of Retepora (Fig. 52), or the branching 
stem of Myriozoum (Fig. 53), may easily be mistaken for. corals, to 
which, however, they are by no means allied. Careful observation has 
shown that the little animals which form these growths, and live together 
Fig. 52. Retepora cellulosa, Fig. 53. Myriozoum truncatum, 
V 2 nat. size. Ya nat. size. 
in colonies, are very different from, and more highly organized than, the 
polypes of a coral. 
The Polyzoa are widely distributed in all seas and present a wonder¬ 
ful variety of forms. A kind very common on the British coast and 
well known to all visitors to the sea-side is the leaf-like growth of 
Flustra, the sea-mat, the colour and texture of whitey-brown paper. 
CRABS, LOBSTERS, SHRIMPS, BARNACLES etc. 
( CRUSTACEA). 
(Tanks No. 6, 7, 10, 11, 20, 22, 23, 24 and 25.) 
These animals form a peculiar and very strictly defined group. 
Contrasted with the quiet and dreamy lives of the brightly coloured 
corals and the annelids, with the monotonous movements of the apathetic 
fishes, and with the lazy mollusks and echinoderms, the active and often 
comical movements of the different kinds of Crabs are very attractive; 
and we soon discover that the mental faculties of these creatures far 
exceed those of most other marine animals. In making this statement 
we have in mind chiefly the short-tailed Crabs and their allies, which 
are found in tank No. 23 ; but as most people are better acquainted 
with the long-tailed Lobster, we begin with the latter, and try to explain 
the other forms by comparison with the better-known animal. 
The Lobster, Homarus vulgaris (Fig. 54), is, on the whole, an 
enlarged copy of the fresh-water crayfish; and visitors will easily recognize, 
from examining the large specimens in the Aquarium (tank 6), what are 
the principal features of its organisation. The body is divided into an 
anterior part, consisting of head and chest, which is really jointed but 
covered on the upper surface by an unjointed shell ( carapace ); and a 
posterior part, composed of a number of rings forming the "tail” of the 
Lobster, which terminates in a fin composed of broad flat plates. The 
