Pulmonata 527 



introduction of the snails, and the leaves, except the lower layer, should 

 remain dry; if this condition prevails molds will be reduced to a mini- 

 mum. Twenty-five Polygyra thyroides, for example, may be kept in 

 such a habitat unless it is used for breeding purposes, in which case it 

 should be occupied by no more than four of these snails. The young 

 snails should be removed to another terrarium as they make their 

 appearance. 



The snails should be fed on a mixture of dry rolled oats and calcium 

 carbonate, the amount of the latter being all that will stick to the oats. 

 Place the dry food on a piece of clean, dry glass at the deeper end of 

 the terrarium. Feed the snails at least every third day and allow no 

 excess food to accumulate. An occasional feeding of lettuce will do 

 no harm. 



A habitat such as that described above is good for more than a year 

 and requires very little attention. The principle in the above example 

 may be applied to terraria of any size ; a single Polygyra thyroides will 

 do very well in a finger bowl terrarium. Finger bowls and evaporating 

 dishes make very good terraria for small forms such as Zonitoides 

 arborea. Clean sand in this case may be substituted for the soil and 

 gravel, and only enough water is added to moisten it. Avoid saturation. 

 Water should not accumulate on the under side of the cover except at 

 times when the terrarium is subjected to sudden changes of temperature. 

 Such accumulations of water in terraria containing small snails imprison 

 and suffocate many of those which try to walk through the drops of 

 water. Terraria should not be kept in direct sunlight. 



VIVARIUM METHODS FOR THE LAND MOLLUSCA OF 



NORTH AMERICA 



A. F. Archer, University of Michigan 



UNDER natural conditions food, shelter, and the chemical con- 

 dition of the soil are very important. In laboratory cultures 

 shelter is not so important as in nature, since it is obvious that laboratory 

 snails will not be exposed to the same degrees of wetting and drying as 

 those in the field. For short experiments a glass aquarium with no soil 

 may be used. It is only necessary to provide sufficient food and mois- 

 ture to keep the snails active. 



The regular vivarium consists of a fairly large aquarium such as is 

 available to those who customarily have cultures of fish and other 

 aquatic forms. The top of the aquarium should be covered with a 

 wire screen, since the larger species are very likely to crawl out. The 

 bottom of the cage should be covered with a layer of soil about an inch 

 thick. This soil should be taken from a woodland if the snails in the 



