CHAPTER XIII 



THE ANIMALS OF THE MARINE AQUARIUM 



WHILE there is almost no part of the British Isles where the 

 teacher cannot keep a freshwater aquarium, at least on a small 

 scale, the marine aquarium, as already indicated, is difficult to 

 manage successfully except near the sea. In spite, therefore, 

 of the fact that our coast-line is relatively enormous, there must 

 be many places where it is virtually impossible. Again, though, 

 as we have suggested, there are a considerable number of fresh- 

 water animals which do not occur in the extreme north, and are 

 common in the south, yet a large number of common forms may 

 be expected in any body of fresh water. In the case of the marine 

 animals, on the other hand, the difference between the species 

 found in the east and the west, the north and the south, is so great 

 that one can make relatively few general statements about rarity 

 or commonness. It is true generally that the western shores, 

 washed by much warmer water than the east, are richer in interest- 

 ing animals than the other parts, and this is especially true of the 

 south-west. On the other hand, the fact, with which everyone 

 is well acquainted, that the northern waters are the richer in food- 

 fishes suggests, what is indeed the case, that those northern 

 waters must also be rich in the organisms on which the food- 

 fishes prey. The sojourner at the sea whose lot is cast on the 

 north-eastern shores is thus not without his compensations. 

 Finally, to obviate disappointment, it may be well to emphasise 

 the fact that at least the majority of the animals which can be 

 made to thrive in an aquarium are the inhabitants of rocky pools. 

 The teacher, therefore, who has available only a long stretch 

 of sandy beach cannot hope to do much in the way of aquarium 

 keeping. It is true that by digging in the sand at extreme low- 

 water quite a considerable number of sand-borers, such as burrow- 

 ing molluscs like razor-shells, cockles, otter-shells, and so on ; 



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