140 MIND IN EVOLUTION CHAP. 



ficant that it finally met with its death by mistaking the 

 thumb. The same author tells a story of an earwig that 

 came regularly for its breakfast. 



Among Cephalopoda there is good evidence of the effects 

 of experience in the form which we are examining. The 

 well-known story of the vengeance of an octopus on a 

 lobster is parallel with the rivalry of the female Paradise 

 fish showing a similar persistence of excitement. 1 It 

 agrees with this that cephalopods should, like fish and 

 reptiles, "know" their keepers, 2 and that they should leani 

 to avoid the stinging sea anemones on the shell of hermit- 

 crabs, and adopt a safer method of procuring them. 3 

 When we descend from cephalopods to other molluscs 

 the evidence for any degree of learning from experience 

 becomes much more scanty. We have seen that snails 

 and limpets have the power of " homing ; " the former, 

 at least, are apparently guided by a trail. It is possible 

 under the circumstances that the whole process may be 

 instinctive. When sated with food, for example, the 

 mollusc may feel a blind impulse to retrace its steps along 

 its trail. 4 Dawson, however, found, among other evidences 

 of past experience, that a snail dropped into an aquarium 



1 Romanes, p. 30 ; Schneider, p. 78. 2 Schneider, loc. dt. 



3 But cf. J. A. B., 1911, p. 399, where some experiments by Polamanti 

 on the cephalopod Elebone Moschata are summarised, which give purely 

 negative results. 



4 There is a story (which has crossed the Atlantic) of a snail which would 

 come at the call of a girl who had trained it to do so, while it shrank from 

 other voices. (Cambridge Natural History, Vol. III. p. 35.) That 

 oysters learn to keep their shells shut out of water for a longer and longer 

 time is well known, but it is not clear to me whether this is due to simple 

 practice each time the thing is done making the next easier or to ex- 

 perience of disagreeable results from opening (see Cambridge Natural 

 History, Vol. III. p. no). Mr. Lonsdale's story of the pair of snails 

 made famous by Darwin is, at least in the interpretation given it, quite 

 isolated. If the observation is correct, I should suppose that the 

 first snail, after feeding, had an impulse to return on its trail to its mate, 

 and that when they started again, the weaker mate being rested, and 

 being also hungrier, was impelled to follow. Of failure to learn on the 

 part of the snail, a good instance is reported by Mobius. A snail 

 attempted to take a piece of meat from a polyp (Actinia mesembry- 

 anthemum\ and coming into contact with the polyp's tentacles, shrank 

 together, and turned away. It returned to the charge, with the same 

 result. This was repeated several times over, till Mobius charitably gave 

 the snail another piece of meat. (Brehm, 2nd edition, X. p. 479. The 

 second half of the story is not given in Brehm's 3rd edition.) 



