96 
THE PEARL OYSTER 
parent vermiform insect moving in the fucus growing on 
the shells of the oysters. I had also taken the precaution of 
covering the mouth of the tumbler with a dinner napkin, so 
that the heat, motion or odour of the lamps, the air, the breath 
might not affect the natural movements of the animal. 
The foot, when contracted in spirits, is seen under the 
microscope to have a median groove throughout its length ; 
but 1 must confess that the animal had been abruptly 
introduced to spirit of full strength and not to gradually 
strengthened spirit. When spread out, however, as it was 
when adhering in life to the glass in the act of walking with 
the sole towards me, and only a very thin glass intervening, 
I made the foot out to have three suctorial disks, answering 
seemingly to the propodiim, mesopodiim, and metapodium 
of the heteropoda, with the median groove apparent only 
between the anterior {propodium) and mid sucker, and the 
mode of progression was this : — While the two posterior 
suckers adhered, the anterior advanced by stretching itself 
out, adhering as it went by both sides of the groove till 
the anterior sucker took a hold ; then the mid sucker was 
loosened and advanced, the anterior and posterior suckers 
and the shell being stationary the while, till the mid sucker 
got a hold nearer to the anterior sucker ; then the posterior 
sucker loosened its hold, the whole shell was given a sudden 
lift, the space between the mid and posterior sucker was 
contracted, and the posterior sucker took a fresh hold closer 
to the mid sucker. The foot was merely contracted as in the 
body of a worm, not brought together in a loop as in a leach. 
Then the process was repeated and the animal moved steadily 
up the smooth glass, with its burden of two other oysters on 
its shell, till it got the point of its tiiubo (beak) level with the 
surface of the water, and there it rested adhering by its foot 
alone without any slired of bi/ssiis. After a little time I 
agitated the water with a fork so as to try and wash it off ; 
1 even touched the shell gently with the fork, but the animal 
