156 INTELLIGENT BEHAVIOUR 
to realize the nature of their experience—to get any adequate 
notion of their mental processes! We are inevitably forced to 
describe their psychology in the most general terms. So, too, 
with forms still lower in the scale of intelligence. Many 
molluscs unquestionably profit by experience. But can we 
clearly picture to ourselves the nature and manner of acquisition 
of this experience ? The way in which limpets return to the 
scars on the rock which form their homes seems to show that they 
have acquired a practically adequate experience of their near 
surroundings. Romanes cites * some of the earlier observa- 
tions which have been extended by Professor Ainsworth Davis.f 
I looked into the matter myself some years ago, at Mewps Bay 
near Lulworth in Dorsetshire. The method adopted {¢ was to 
remove the limpets from the rock, and affix them at various 
distances from their scars. This can be done without difficulty 
or injury to the mollusc if one catches them as they are moving. 
But one must make sure that they are just leaving or returning 
to their proper homes, and are not taken in the midst of a 
more extended peregrination, as in that case their special scars 
cannot be noted. Failure to be careful in this matter vitiated 
my earlier observations, which are therefore excluded in the 
following table :— 
Number returned. 
Number Distance 
removed. in inches. 
| In 2 tides. In 4 tides. Later. 
25 6 21 _ “= 
21 12 13 5 — 
21 18 10 6 2 
36 24 1 1 3 
From the nature of the rock surfaces the removal of a 
limpet to a distance of two feet almost invariably involved 
placing them on the further side of an angle. And though 
some returned over such an angle, the majority did not. 
* « Animal Intelligence,” pp. 28, 29. t+ Nature, vol. xxxi., p. 200. 
f Wbid| vol. li.; p. Lai. 
