HABITS OF THI LIMPET. 99 
on numerous specimens of various sizes, completely confirm Mr. 
King’s opinion, and the method of marking rendered cases of 
“mistaken identity” quite out of the question. ‘I'he greatest 
distance from its scar at which I noticed a marked limpet to be 
was about three feet; yet this distance, though extremely rough 
and covered with barnacles, was re-traversed without difficulty. 
The excursions from the. roosting-places were made in any 
direction where food offered; so there were nothing like beaten 
tracks formed. But a limpet always returns home before the 
rising tide reaches it, and invariably roosts with its snout 
pointing in the same direction. As might be expected, this 
direction is only constant for individuals. As the shape of the 
sear corresponds exactly with the shape of the shell, comfort, of 
course, could only be gained and a firm hold effected by limpets 
roosting permanently in the same direction on their scars. 
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-organised an animal, 
very keen. The 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 extremely 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 confused 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 opera- 
_ tion 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 it, and it occurred to me that 
one reason why limpets kept 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 and the 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 
