40 An Observation on Mind in Molluscs. [Sess. 



altogether. I took it out and placed it upon a stone, where 

 it remained the whole evening motionless ; by the morning it 

 had probably recovered from its excess, for it had disappeared. 



I now saw a large black snail 8 or 10 feet away, crawling 

 slowly up a walk in the direction of the bowl. As twilight 

 was approaching I did not feel inclined to wait and see the 

 result, and to save the snail the trouble of travelling so long a 

 journey I removed the bowl to a place about a foot away from 

 it, placing it at a right angle to the snail's path, so that it 

 would have been naturally passed by. The snail stopped and 

 remained in the same place for at least twenty minutes. The 

 evening was quite still, so that the wind did not blow smells 

 in one direction more than another. This was the period of 

 deliberation, to use a human expression. The snail was 

 taking its bearings. " There is a delightful odour about — 

 where can it be ? " In another half hour this, the fourth, 

 mollusc had found the nectar. 



I presume that what may be called mental operations pro- 

 ceed very slowly in animals much lower than man, and this 

 long period of deliberation, as I have called it, reminds me of 

 a similar phenomenon I have observed in frogs. I have some- 

 times kept frogs in a greenhouse and fed them with worms. 

 On giving a frog a worm on a stick, at times when it must 

 have been very hungry, I have seen it stare at the worm for 

 two or three minutes. The mental operation the frog was 

 performing, translated into a human form of thought, was 

 most likely this — " That looks like a worm, but what a queer 

 place for a worm to be, wriggling on the end of a stick." 

 Finally froggy makes up his mind that it must be a real 

 worm, his tongue darts out like lightning, and the end of the 

 worm is down his throat in an incredibly short time. 



Later in the evening, I found that other two slugs had 

 found their way into the bowl — six in all had been attracted 

 to it in a couple of hours. 



There are so few observations on record of the intelligence 

 of the mollusca, I have thought it worth while to lay these 

 before you. They show a considerable amount of intelligence. 

 The essential purpose (I suppose I must ask pardon for using 

 the word purpose in speaking of physiological things, but I 

 do not know a better word) — the primary purpose of a sense 



