172 



Aquatic JLitt 



red progeny results ; but I am not able 

 to say to what extent this agrees with 

 the Mendelian theory. Continual mating 

 of the red considerably improves the bril- 

 liance of color. As before remarked, 

 this red form is a sort of albino. I have 

 been unable to find any satisfactory lit- 

 erature dealing with albinism in the low- 

 er animals ; even the best authorities on 

 fishes dismiss the subject with few 

 words, and no attempt at explanation. 

 Certainly, departure from the normal is 

 productive of much change in the tem- 

 perament of albinos and transitory al- 

 binos. They become more easily tamed, 

 and lend themselves to domestication. 

 The observation of a normal green and 

 a golden tench is quite an object lesson, 

 they differ in habits entirely. Also the 

 difference of character exhibited by a 

 golden and a white orfe will be instruc- 

 tive, as this carries albinism a stage 

 further ; nothing need be said of goldfish. 

 In this way, the red Planorbis shows evi- 

 dences of capabilities of domestication 

 unknown in the normal. 



Those of you who have read Fabre's 

 monumental observations on insect life, 

 will have been struck with the difficulties 

 he encountered when trying to induce a 

 lowly creature to vary its procedure in 

 opposition to its instinctive habits. Other 

 observers have claimed successes in over- 

 coming the persistent efforts of these ani- 

 mals to retain their instinctive habits, and 

 you will agree with me that it is highly 

 desirable such observations should be 

 carefully confirmed in every detail, be- 

 fore being brought forward as facts. It 

 is obvious there must be some limit to 

 animal resources, and that the creature 

 only succumbs to interference when cer- 

 tain secretions become exhausted, and 

 the animal is compelled to give up the 

 struggle. Freshwater snails have an in- 

 telligence, and are capable of being 



taught to acquire knowledge apart from 

 instinctive habits. The acquired can be 

 interfered with without resentment, as 

 snails in general are quite good tempered 

 creatures ; but when an effort is made to 

 turn a snail aside from its instinctive de- 

 sires, grave difficulties arise. 



For the study of the freshwater snails 

 small aquariums are not to be recom- 

 mended. I find, I get the best results in 

 a bell glass nearly 30 inches in diameter, 

 the bottom filled with a mixture of sand 

 and shell grit up to where the sides be- 

 come vertical, and having a depth of 

 about 20-in. of water. Such an aquarium 

 should contain well established and grow- 

 ing plants — Vallisneria for choice, and 

 should be capable of being rotated or in- 

 spected all round. 



Jeffreys says, "Land and freshwater 

 snails, as well as slugs, are for the most 

 part herbivorous," also, "Several kinds 

 of Planorbis (freshwater snails) yield, 

 on being irritated, a quantity of their own 

 purple blood ; these are vegetable eaters." 

 In the face of these definite declarations 

 I feel some diffidence in raising objection 

 to the accuracy of the statements ; but I 

 must, in the interests of truth, say that 

 Planorbis corncus, and probably some 

 others, are more carnivorous than herbi- 

 vorous. In fact, I can scarcely imagine 

 cornens being a vegetarian, if animal 

 food is obtainable. In a pond there must 

 be constant deaths of minute animals, 

 and unimaginable numbers of tragedies 

 from which the mollusc may obtain some 

 share, and never be at a loss for animal 

 matter. During the warm weather 

 Planorbis c omens will devour incredible 

 quantities of animal food, and it will 

 grow faster and do better on a flesh diet 

 than on vegetation. I have fed it upon 

 animal food exclusively, tough muscular 

 table scraps, and I have made every ef- 

 fort humanly possible to deprive it of 



