50 INTRODUCTION TO ZOOLOGY CHAP. 



the anemones can attach themselves at different levels. When 

 this has been done satisfactorily, the sea-water may be added ; 

 this can be obtained, in convenient small barrels, from the Salt 

 Water Department, Great Eastern Railway, Liverpool Street 

 Station, at a cost of 6d. for three gallons. In pouring the 

 water in, it should be directed on to a large rock or an inverted 

 saucer placed on the bottom, in order to avoid stirring up the 

 sand. 



The tank is not yet ready for its animal inmates ; healthy, 

 growing seaweeds should next be introduced, for they will, in the 

 process of assimilation peculiar to plants, aerate the water, keeping 

 it so pure that it rarely needs to be changed. The seaweeds 

 should be carefully chosen, only healthy plants attached to pieces 

 of rock, shell or wood, being introduced into the tank. The 

 different species of the bright green Ulva, or sea-lettuce, are excel- 

 lent forms to have, or the dark-green, hair-like Cladophora ; also a 

 growing clump of one of the beautiful branched red seaweeds will 

 add to the beauty of the tank, though they are not so effective as 

 the green forms in aerating it. 



The aquarium should stand, if possible, in a north window, so 

 that it gets plenty of light, and yet not the direct rays of the sun, for 

 these cause the too rapid development of microscopic green Algae 

 over glass and stone. If this superfluous green should develop, a, 

 few common periwinkles, placed in the tank, will probably soon 

 devour it. Three sides of the tank should be shaded with a dark 

 curtain, and the top should be covered with glass, so that dust does 

 not collect and form a scum over the surface of the water ; it is 

 well to beat the water with a piece of wood every day, in order 

 to drive air down into it. As the water evaporates, sufficient 

 fresh, rain or tap water must be added, to keep the density of the 

 water constant. This should be poured in, very gently, a little 

 at a time, and then at once mixed with the salt water by stirring 

 it with a glass rod. 



When all is ready, the desired inmates of the tank may be 

 introduced into it. It is important not to overcrowd the space, 

 and also to choose those anemones that thrive well in captivity. 

 Most hardy kinds travel with impunity, just packed in a tin with 

 plenty of damp seaweed bladderwrack makes good packing but 

 it is of course better, if possible, that they should be sent in a jar 

 of sea -water. When they arrive they should be put first into a 

 " quarantine " bowl of sea-water, supplied with plenty of rocks or 

 stones to which they can fix themselves, and only those should be 

 introduced into the large tank which appear quite healthy and 

 attach themselves to some support. 



