MOLLUSCA. 27 



release them, that natural selection would have developed 

 a special instinct to try pulling successively in three 

 directions at right angles to one another. 



The only other instance that I have met with of the 

 apparent display of intelligence in snails is the remark- 

 able one which Mr. Darwin gives in his ' Descent of Man,' 

 on the authority of Mr. Lonsdale. Although the inter- 

 pretation which is assigned to the fact seems to me to go 

 beyond anything that we should have reason to expect of 

 snail intelligence, I cannot ignore a fact which stands 

 upon the observation of so good an authority, and shall 

 therefore quote it in Mr. Darwin's words : 



These animals appear also susceptible of some degree of per- 

 manent attachment : an accurate observer, Mr. Lonsdale, in- 

 forms me that he placed a pair of land-snails (Helix pomatia), 

 one of which was weakly, into a small and ill-provided garden. 

 After a short time the strong and healthy individual disap- 

 peared, and was traced by its track of slime over a wall into an 

 adjoining well-stocked garden. Mr. Lonsdale concluded that 

 it had deserted its sickly mate ; but after an absence of twenty- 

 four hours it returned, and apparently communicated the result 

 of its successful exploration, for both then started along the 

 same track, and disappeared over the wall. 1 



In this case the fact must be accepted, seeing that it 

 stands on the authority of an accurate observer, and is of 

 so definite a kind as not to admit of mistake. Conse- 

 quently we are shut up to the alternative of supposing 

 the return of the healthy snail to its mate a mere acci- 

 dent, and their both going over the wall into the well- 

 stocked garden another mere accident, or acquiescing in 

 the interpretation which Mr. Darwin assigns. Now, if 

 we look closely into the matter, the chances against the 

 double accident in question are certainly so considerable 

 as to render the former supposition almost impossible. 

 On the other hand, there is evidence to prove, as I shall 

 immediately show, that a not distantly allied animal is 

 unquestionably able to remember a particular locality as 

 its home, and habitually to return to this locality after 

 feeding. Therefore, in view of this analogous and cor- 



Desccnt of Man, pp. 262-3. 



