° 
1885.] Fsychology, 521 
The question now arises, what sense is employed by the limpet 
in finding its way back to its scar? The appreciation of locality 
displayed is certainly, for so simply-organized an animal, very 
e sense of sight is, evidently, out of court, for an eye 
like the limpet’s, consisting of no more than a sensitive cup, could 
do little if any more than distinguish between light of different 
degrees of intensity. The tentacles seemed at first sight to be ex- 
tremely likely organs to use for the purpose, and to decide this I 
excised those of two marked individuals, which were off their 
scars. One speedily found its way back; the other seemed con- 
fused by the operation for several days, but after that time was 
found on its scar, This shows a remarkable power of memory, 
unless the scar was found by accident, which is possible, as the 
individual was near home when the operation was performed. 
But even in that case the scar must almost certainly have been 
remembered. Thus the tentacles do not seem to be the means by 
which home is returned to. The sense of smell then suggested 
itself, and it occurred to me that one reason why limpets keep on 
their scars when covered by the water was to prevent the “ scent” 
of the track traversed from being washed off. With a view to 
determine this the space between a wandering limpet and its scar 
was carefully washed again and again with sea-water. In spite 
of this the limpet in question readily found its way back again. 
Further experiments are, however, needed, on this head, for any 
ordinary washing would be very ineffective compared with the 
rolonged soaking the tide would effect in the case of a limpet 
(like the one just mentioned) living some distance below high- 
water mark. Still some limpets live so near this last that they 
are covered but a very short time, and yet these remain on their 
scars during that time. Hence I think some other motive 
ably induces them to remain firmly fixed to their scars when 
under water. Of course they can hold on best when so fixed, 
and this suggests the most likely reason for the habit, z.e., to avoid 
