166 FEESH-WATEE AQUAEIA. 



This band is known as the lingual ribbon or toothed tongue. 

 The lingual ribbon is not only very interesting, especially xmder 

 the microscope, but it is also useful in helping to determine 

 the genera of various individuals. Some snails have a great 

 number of teeth. The teeth are ari-anged on the lingual ribbon 

 in rows, which vary in number and order according to different 

 genera. 



SnaUs, when kept in confinement, frequently deposit their 

 eggs upon the transparent sides of the tank, thus giving the 

 aquariimi-keeper an opportunity, by the help of a magnifying 

 glass, of watching the development of the ;Pry. Soon after the 

 eggs are laid, a small speck may be seen close to the side of 

 each egg; as this speck grows it will gradually work its way 

 into the middle of the egg, and then it contiaues to increase 

 in size and in power of movement, until it breaks the egg-sac, 

 and becomes free. When the young snails are hatched in an 

 ordinary aquarium they generally fall victims to some of the 

 watchful fish. Should it be wished, however, to rear the snails, 

 it will be necessary to transfer the eggs to a small and shallow 

 aquarium well stocked with growing weeds and confervse, and 

 where there are no fish or any other visible animals. This 

 may easily be done by removing those portions of weed or 

 pieces of stone upon which the ova have been deposited. The 

 flat floating leaves and long stalks of the Cape Fragrant Water 

 Lily seem to have great attractions for the snail which is 

 desirous of depositing eggs. 



When the ova are hatched and the fry have gi'own sufiiciently 

 — say so large that they can be easily picked off the plants 

 with the finger and thumb — ^they may be returned to the 

 aquarium. Snails grow slowly, and it is sometimes about two 

 years before they arrive at maturity. As the young snail 

 grows it enlarges its shell according to its wants. This is 

 done by adding a small portion of mucous secretion to the 

 edge of the shell, and when the secretion is dry it is followed 

 by some more, but this time it is mixed with carbonate of 

 lime. The first secretion makes what is called the epidermis 

 of the shell, while the second forms the shell itself. These 

 additions go on from time to time until the animal is full- 



