LEAPING OF STROMB (STROMBUS GIGAS LINN.) 207 



As compared with other gastropods, Strombus is remarkably 

 alert and active, and in the quickness of its movements it reminds 

 one more of a vertebrate than of a mollusk. Its eyes, too, are 

 highly developed and are moved and directed in such a way as 

 to give it the appearance of no small degree of intelligence. 



After the stromb has protruded its foot a few times in a tenta- 

 tive way, it will gradually extend this organ till it reaches the 

 substrate. The anterior finger-like end of the foot is then pressed 

 vigorously against the ground, the middle section of the foot 

 arching over to the metapodium, which together with the oper- 

 culum is moved in under the shell and thrust vigorously back- 

 ward. At the same moment the general musculature of the foot 

 and of the body contracts in such a way as to raise the shell over 

 the support given by the foot and throw the shell vigorously 

 forward, as though the animal as a whole made a spring (fig. 2). 

 After such a leap, which, as already stated, may be half the 

 length of the shell, the animal usually withdraws a little, then 

 thrusts out the foot far forward, regains a hold on the substrate, 

 and leaps again. Thus step by step it progresses at a rate quite 

 surprising for a mollusk. 



The principle upon which the locomotion of Strombus rests 

 appears to be the forward extension of the body and especially 

 the foot, the attachment of the latter by its two ends to the sub- 

 strate, and the lifting and throwing of the shell forward to the 

 advanced location occupied by the foot. In preparing for a leap 

 the anterior finger-like end of the foot is closely applied to the 

 substrate and appears to attach itself by suction. Such, how- 

 ever, is not the case. ^Tien a stromb is about to spring, its 

 shell may be laid hold of by the experimenter without interrupt- 

 ing the action of the animal, and under such circumstances the 

 anterior end of the foot may be freely lifted from the substrate, 

 showing that it is not exerting suction, for this end leaves a mud, 

 wood, or glass surface at once and without the least sign of being 

 especially attached. The posterior end of the foot, which at the 

 moment of the spring is drawn well under the shell, is fixed by 

 having the point of the operculum energetically driven into the 

 substrate. So vigorous is this backward thrust of the operculum 



