Tanks No. 21 and 22. 
35 
metamorphosis change into the worm-like animal and encase themselves 
with a tube. 
Besides these tube-inhabiting Annelids, of which all the warmer seas 
possess a variety of beautifully coloured forms, there is a second group, 
no less rich and varied; the free-living Annelids. 
The Bay of Naples has long been celebrated among zoologists as 
one of richest localities for these worms, and up to the present date 
already (including the tube-inhabiting worms) about 300 different species 
have been described. Still only a small portion are suitable for the 
purposes of an Aquarium, as most of them live secluded in the mud or 
in the cracks of the rocks. One of the finest is the Sea-mouse, Aphro- 
dita (Fig. 50), the bristling coat of which reflects with a bright metallic 
lustre all the colours of the rainbow. 
Its nearest relation is the very common Hermione , which in spite 
of its beautiful name is a disgusting animal, the hooked spines of which 
Fig. 50. Aphrodita aculeata, l /% nat. size. 
Tank 22. 
Fig. 51. Ale top a Cantrainii, 
V 2 nat. size. Tank 20. 
penetrate into the hand that touches them, and cause inflammation. Alciopa 
(fig. 51) is as transparent as the jelly-fish and other pelagic forms, and 
like them lives near the surface of the sea. It is rarely seen in the 
Aquarium (Tank 20), since the capture of such animals, as already 
mentioned, depends so much upon the weather (see p. 26). 
The Annelids have lately become a special field of study among 
zoologists, since their comparative anatomy has revealed features which 
support the theory of their relationship to the Vertebrates. At present 
a lively scientific controversy is being carried on with regard to this 
moot point. 
P0LYZ0A or BBY0Z0A. 
(Tank No. 21.) , 
The name Polyzoa , i. e. multiple animals, was given to this group 
from the fact that they live in large colonies, like the corals. By the 
German school they are always called Bryozoa or moss-animals, a name 
which arose from the moss-like or coral-like growths which these 
colonies form. 
3* 
