150 DIVERSIONS OF A NATURALIST 



paler, nor are the red corpuscles shed during the great 

 distensions and contractions of the body. Measurements 

 were made to determine the removal of water from a 

 glass jar by an expanding sea-snail, and it was found 

 that none is removed or taken up ; in fact, the whole of 

 what is very often an astonishingly large and bulky 

 distension of the foot, or of lobes of the body, and the 

 subsequent rapid shrinking of the same parts, depend 

 entirely on the blood being injected from the rest of the 

 body into the swelling part, and squeezed from it into 

 the depleted region when the swollen part shrinks again. 

 The firm, opaque shell hides from view the change of 

 shape of the concealed body, and we see only the dis- 

 tended foot or other lobes which project from the 

 shell. 



The cockle has a " foot " of a very curious scythe-like 

 shape, usually carried bent up between the two valves of 

 the shell. Those who rightly like to confirm statements 

 about unfamiliar animals can do so by buying a cockle 

 or two at the fishmonger's. Some bivalves (the Noah's- 

 ark-shell, called " Area," and a few others) have a great flat 

 foot, like that of the univalves, and crawl about on it. 

 But in most bivalves it is curiously elongated and 

 modified, for the purpose of burrowing into sand by 

 vigorous strokes, and in some it is suppressed altogether, 

 as in the oyster. The cockle is remarkable for the fact 

 that when placed on a board or a rock it will give such a 

 vigorous kick with its bent foot as to throw itself up 

 a yard or so into the air. A naturalist (Stutchbury) 

 dredging in Port Jackson, Australia, many years ago was 

 overjoyed at discovering in his net three specimens of a 

 very peculiar kind of cockle (Trigonia), which was till 

 then only known in the fossil state from the oolite strata 

 of Europe. He placed the three novelties on the seat of 



