CHAPTER XII 



THE ANIMALS OF THE FRESHWATER AQUARIUM 



i. The Vertebrates. None of the aquatic mammals or birds 

 can be said to be available for the purposes of the indoor 

 aquarium, whatever may be done in the open. Nor have we any 

 native aquatic reptiles available. There is, however, one Euro- 

 pean form which is worth mention, because it can sometimes 

 be obtained from dealers at no great outlay. This is the pond- 

 tortoise (Emys europea), now restricted to Southern and Middle 

 Europe, though it occurs as a fossil in peat deposits in the east of 

 England. It is much less commonly seen than its relative the 

 Greek tortoise, so frequently sold in the streets, but is not very 

 rare as a pet in this country. 



The pond - tortoise usually measures about five inches in 

 length, and is thus smaller than the Greek tortoise, from which 

 it also differs in its webbed feet, which adapt it for an aquatic 

 life. The shell is either spotted with yellow on a dark ground 

 or shows radiating lines. The diet is purely animal, so that the 

 pond-tortoise should not be kept in an aquarium containing 

 fish or tadpoles, or even insects, unless these can be sacrificed 

 to its appetite. It will also eat meat in captivity, and should 

 be given an opportunity of leaving the water occasionally. The 

 winter is normally passed in hibernation in the mud at the bottom 

 of the pond. The eggs are laid on land, the female digging a hole 

 in the earth near the pond for the purpose. 



As regards the structural points which may be observed in the 

 animal, one would notice first the scales which cover the bones 

 of the shell as well as the exposed parts of the body. The tor- 

 toiseshell of commerce is obtained from the scales of a turtle, 

 the scales being thin plates of horny tissue quite comparable in 

 structure to the scales of a snake. The " shell " proper of the 

 pond-tortoise is a bony structure, lying beneath the scales, 



