3o8 kf:w : the faculty of homing in gastropods. 



In the absence of experiments of a definite nature, Mr. Romanes 

 admits that nothing can be said in regard to this faculty except 

 that it exists, yet he is not driven to Professor Hackel's conclusion 

 that the same is due to an additional and inexplicable sense.* It is 

 interesting to find that Sir J. Lubbock, after his experiments with 

 Hymenoptera, agrees with Mr. Romanes that there is no sufticient 

 evidence of such an additional sense in insects, t some of which, as is 

 notorious, exhibit a wonderful way-finding faculty. Seeing how readily 

 slugs, snails, whelks, etc., find their food, and that this is thought to 

 result in great measure froni the extreme delicacy of the sense of smell, 

 it occurred to me that such animals might possibly be able also to 

 scent their hiding-places, and follow their own trails, and find and 

 track each other by smell. The spot frequented by a slug or snail 

 would doubtless be bedaubed with the animal's slime and probably 

 with faeces, and therefore might be scented at some little distance. 

 Nevertheless, judging from the observations quoted by Mr. Romanes, 

 and from the additional facts referred to below, there can, I think, be 

 no doubt that a capacity for remembering locality and direction does 

 exist in certain gastropods. It would, however, be impossible in 

 some cases to say to what extent the animals are guided by smell ; 

 probably they often rely partly upon this sense and partly upon 

 memory. That they may be guided home by the scent of the 

 outward trail will have occurred to many ; and an individual of the 

 Great Grey Slug has been found to be in the habit of going out and 

 returning along -the same track. In the two instances, however, in 

 which I have seen slime-trails which have started and terminated at 

 the same place the outward and homeward journeys have been quite 

 independent one of the other, and Mr. C. Ashford tells me that his 

 observations tend to show that a snail, on returning to its hiding-place, 

 is not bound by necessity to the old track. The space between 

 a wandering limpet and its scar, and the scar itself, have been 

 thoroughly washed many times with sea-water, but this did not 

 interfere with the due return of the animal. 



By returning from time to time to a fixed resting-place, a limpet 

 is enabled to form a socket or scar having irregularities corresponding 

 to the serrations in the edge of its shell, or to adapt the shell during 

 growth to the uneven surface of hard rocks, and the security thus 

 obtained must be of great importance to an animal much preyed 

 upon by sea-fowl and other enemies, and which often has to resist 

 heavy breakers. A terrestrial gastropod, if devoid of memory, might 

 often fail to obtain shelter, and fall an easy prey to its diurnal 



* ' Mental Evolution,' p. 95. 



t ' Senses, instincts, and intelligence of Animals, 2nd ed., 1SS9, p. 271. 



Naturalist, 



