514 Miss Hilda M. Bishop on the 



3. Trochi/s crassus and T. ziziphinus, alive and in section. 



4. Paludina vivipara, alive, by dissection, and in section. 



5. Littorina litovea, L. obtusata } and L. rudis, alive and 



in section, L. litorea also by dissection, and Lacuna 

 alive. 



6. Cupra-a pyrurn and C. europcea, the former by means 



of dissection and by series of sections, the latter 

 living and by series of sections. 



The Gastropod foot has been studied by most observers 

 from the point of view of its function as a creeping-organ. 

 It is with certain subsidiary functions of the foot, such as 

 adhesion at rest, retraction into the shell, &c, that these 

 notes are chiefly concerned. 



With regard to creeping, from my observations I am led 

 to believe that the manner in which it is effected is somewhat 

 as follows : — 



The front part of the foot is extended forwards by the 

 pumping of blood into that region, and also by contraction of 

 the transverse muscle-fibres, which causes the stretching of 

 the longitudinal fibres and narrows the foot. The contrac- 

 tion of these transverse muscle-fibres and that of the oblique 

 muscle-fibres causes the formation of furrows in the creeping 

 surface of the foot, and the forward extension of the foot 

 gives to the fibres which lie perpendicular to that surface an 

 oblique direction forwards. These perpendicular fibres 

 contract, and the result is the bringing forwards of the 

 visceral mass and at the same time the restoration to these 

 muscle-fibres of their original direction vertical to the sub- 

 stratum, but at a point in front of the original one. The 

 contraction of the longitudinal fibres brings the hinder part 

 of the foot forwards, and restores to the transverse fibres their 

 full length, so broadening the foot-sole. This completes the 

 cycle, which then starts afresh. 



I cannot agree with Biedermann's opinion (1905) that the 

 longitudinal muscle-fibres are all-important in creeping. In 

 the same paper he says that, if only the head-end of the foot 

 of Helix touches a glass plate, there immediately arises a set 

 of locomotor waves in the foot-sole, which spreads to the 

 parts not in contact, but no such system arises if even as 

 much as half of the hinder end of the foot touches the plate 

 when the head is not in contact. This hints that though the 

 waves appear at the back end of the foot and travel forwards, 

 yet they have their origin in the head region, i. e. they are 

 controlled by the nerve-centres there. To Haliolis, however, 

 this description does not apply, for very often this form 



