MOSS CORALS. 133 



identified, and we looked and looked again with increasing plea- 

 sure at our first specimens of Moss Corals. 



It has been usual, until of late years, to rank these animals 

 with the Hydraform Polyps, to which in external form and ap- 

 pearance they have a strong resemblance ; but more careful re- 

 search has shown that they possess a far higher type of organiza- 

 tion than the Polyps, and that their true affinities are with the 

 great Molluscan sub-kingdom. There is a great diversity in the 

 form and arrangement of the cells of the different species of 

 Bryozoa, although there is but little difference in the form and 

 structure of the animals themselves. In all of them alike there 

 is a complicated and highly elaborate digestive apparatus, to 

 which access is had by a sensitive and contractile gullet, situated 

 at the bottom of the funnel or bell-shaped circle of tentacles. 

 These organs are rigid bristle-like bodies, incapable of contraction, 

 and beset on their inner side with a double row of vibratile cilia, 

 upon the action of which, in producing a vortex in the water, and 

 so bringing it food, the animals depend for their subsistence. 



It is an extremely interesting sight to watch the behaviour of 

 these tiny creatures when with a pocket lens and a good light 

 you. get them well into view. We will suppose that on the pro- 

 jecting corner of a block of stone, covered with the delicate lace- 

 work of their clustering cells, a hundred or more of the little 

 funnel-shaped circles of tentacles are seen upstretched. A t first 

 sight all seems still and absolutely motionless ; but in a moment 

 you perceive one and another suddenly starting and half closing 

 their tentacles. In a moment more, and with a steadier look you 

 see the floating atoms in the water above whirling and dancing 

 round, and hurrying towards the bottom of the funnel, where the 

 mouth perceptibly dilates to receive them. But not unfrequently 

 atoms unsuitable for food are brought by the ciliary currents as 

 well as acceptable provender ; against these the mouth keeps reso- 

 lutely closed, while the tentacles twitch and start, and make great 

 efforts to shoot them forth out of the way, sometimes struggling 

 quite convulsively in the endeavour, BO as to suggest to the 

 observer that the little creatures are positively in danger of choking. 



The Mollusca, to which the Bryozoa introduce us, are not, 

 generally speaking, very well adapted for the Aquarium. There 

 are some few species, however, which are extremely useful, and 

 which may be looked upon, indeed, in some sort as the local Board 



