Aquatic TLitt 



175 



little fish and tadpoles, and devours them. 

 It is much sought after by the larger 

 fishes, which take it greedily. It is com- 

 mon to see this snail just above the 

 water line ; but in every case I have in- 

 vestigated, it has been there to escape its 

 enemies, and not from choice. When- 

 ever this snail is found out of its element 

 it is almost a certainty that the water, 

 if good, contains predatory fishes. I have 

 experimentally kept a number of speci- 

 mens of L. pereger in a tiny dish, 2V2 

 inches in diameter, containing under one 

 inch of water, for some months. When 

 first introduced, they all escaped over the 

 edge in the night once, and one individual 

 twice, and then settled down. 



L. pal list ris behaves in much the same 

 way in shallow water. 



Snails subjected to constant transfer- 

 ence from one vessel to another, get ac- 

 customed to changes, and make no at- 

 tempt to escape. The various species of 

 freshwater snails seem able to live to- 

 gether, in harmony, perhaps with one ex- 

 ception. Some time ago I placed a half- 

 grown L. pereger in a small vessel with 

 two dozen P. corneus, about two months 

 old. Within twelve hours all the latter 

 were dead, and I have not repeated the 

 experiment. 



Bateman in his book, "Freshwater 

 Aquaria," says that Neritina fluviatilis 

 will not live in confinement, and men- 

 tions the matter in order to save this 

 snail unnecessary suffering. I have re- 

 cently had a letter from a correspond- 

 ent of repute, who tells me this snail has 

 thrived for years in an aquarium. It is 

 highly important that causes of failure 

 should be sought for before definite 

 statements are recorded. 



As I have a good many Planorbes col- 

 lected for me, I receive quite a number 

 with injured shells, and consequently 

 subjects for observation. Every injured 



snail I have had has been given a chance 

 to live, and has been observed closely. 

 P. corneus is seldom able to repair a ser- 

 ious fracture. Recently I have observed 

 one replace quite a large piece of the 

 outer lip, and in another case a brave but 

 vain attempt was made to replace nearly 

 the whole of the large whorl. In most 

 cases a tiny fracture of the outer lip is 

 given up in despair, and the animal dies. 

 A fracture of the outer whorl, large or 

 small, behind an intact orifice, corneus is 

 utterly unable to repair. I have wit- 

 nessed many attempts, and the animal 

 always dies. A great many of the pond 

 snails are eroded in numerous small 

 spots, which in time become perforations, 

 and in some instances mere pinholes. 

 The death of the snail always ' occurs 

 when the perforation becomes complete, 

 no matter where situated. From this evi- 

 dence, it is very strange to find the eroded 

 apex of the red form so well mended as 

 previously described. 



As to the enmity of the Cypridae; this 

 is a carefully ascertained fact, confirmed 

 by very many experiments, and is quite 

 beyond doubt. The matter can be easily 

 put to test by taking some snail spawn 

 and the weed to which it is attached, 

 and placing this in a bowl together with 

 Cypris, collected from a ditch. A control 

 experiment should be made, carefully 

 eliminating the crustacean. Cypris is al- 

 most ubiquitous ; it makes its appearance 

 even when the utmost care is taken to 

 guard against it. There are numerous 

 species of theCypridae, and I am not 

 prepared to admit that all are sinners. I 

 prefer to suspect the smaller kinds, but 

 in any case, the enemy is the one that 

 is nearly always present. The larger 

 kinds seem to be ignored by the snails. 

 It is still a matter of doubt as to what 

 takes place. From observations I have 

 repeatedly made, I find the snails usuallv 



