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shown at a, the oesophagus at b, the stomach at c, the intestines at d, the muscles at e, the mouth at hh, the withdrawn tentacles at i, the lophophore, or crest-bearer," which is covered with cilia, at m. The same kind of horse-shoe shaped lophophore, or crest, surrounds the mouth of Plumatella.

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Fig. 96.

Cyclops, showing female with egg-bags; the young, and a singlejointed antenna.

Cyclops and water fleas (Daphnia) ought to be encouraged in every fresh-water aquarium. Their food. consists chiefly of decomposing aquatic vegetation, desmids, &c., whilst their own wonderful powers of reproduction will always people the water with living food for the higher animals. Most fishes and amphibians live to a very great extent upon these creatures. Cyclops (Fig. 96) is a very common aquatic object, and the female may be seen with the naked eye. So prolific is she that it is stated she

would be the progenitor of four millions and a quarter of young in twelve months, if undisturbed. Her motherly devotion is seen in the way in which she swims about with her purse-like egg-bags trailing behind her. The young are ludicrous objects, with nothing of the gracefulness of their parents. They have a crab-like form, which indicates their crustacean belongings, and they move about in the most cranky, jerky manner it is possible to conceive, like the big seconds finger of a large clock.

Both Cyclops and water fleas (Daphnia) have such a transparent skin that we can see their internal organs, and watch them fulfilling their several functions. As is the case in most insects, the female is larger in size than the male. These creatures are

a very old race, for we find them fossilised in carboniferous shales in such prodigious numbers that we feel assured they must have bred as plentifully millions of years ago as they do now, when they not unfrequently darken the water of our ponds with their countless crowds. During entire geological periods they have been the food-stock of fresh-water and marine fishes alike, and we find them adapted to all conditions of aquatic life.

Space forbids us to notice other common microscopic objects which may be readily introduced into the parlour tank, and kept ready for observation. They might thus while away many an hour of gloom and perchance of sickness or sorrow; and cannot fail to add another element of interest to aquarium keep

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ing. The two powers which move the human world, love and hunger, seem to reign quite as predominantly

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among animalcules.

Water flea (Daphnia pulex) male, enlarged to corresponding proportion as Fig. 97.

It is not "live and let live,"

however, which is their rule; but "might is right!"

The weakest are constantly going to the wall, with a vigour in which there is no room left for pity, except in the soul of the beholder! May not that be the case with ourselves, and the Great Power whose wisdom has called us and them alike into existence, to fulfil some inscrutable but all-wise purpose of his own?

PARLOUR AQUARIA.

139

CHAPTER IX.

MARINE AQUARIA FOR ROOMS. SEA-WEEDS
FOR DITTO.

THERE are undoubtedly greater difficulties attending the healthy maintenance of small marine tanks in rooms than fresh-water ones; but some of these difficulties vanish before a little common-sense treatment and knowledge of the habits of the creatures we endeavour to keep. As a rule the marine aquaria kept in houses are on too small a scale, and there is the unconquerable tendency on the part of their owners of putting as many objects in them as they possibly can. There is really no reason why small marine tanks should not be kept in a good condition for years, provided they are attended to, say as we should attend to poultry, rabbits, guinea-pigs, canaries, or any other pets we are rearing under semi-artificial conditions. If these are neglected, everybody knows the consequences; and we cannot expect that healthy aquaria can be maintained and neglected at the same time. Indeed, considering how altered are the circumstances under which they live, the wonder is that the inhabitants of aquaria give so little trouble.

In constructing small tanks to hold sea water the

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