CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE MUSEUM OF 
COMPARATIVE ZOOLOGY AT HARVARD COLLEGE. E. L. MARK, Dresctor. No, 231. 
THE MECHANISM OF LOCOMOTION IN GASTROPODS 
G. H. PARKER 
INTRODUCTION 
The snail’s foot in locomotion is so striking and so easily ob- 
served that it has excited the interest of naturalists for a long 
time and yet a complete solution of even the mechanical prob- 
lems connected with its action seems not to have been attained. 
Within recent times a number of investigators have attacked 
the problem of locomotion in snails, but their efforts have been 
directed chiefly toward the elucidation of the action of the neuro- 
muscular mechanism rather than toward an understanding of 
the external mechanical conditions that accompany locomotion. 
It is the object of this paper to consider, in the light of the more 
recent investigations and from the standpoint of renewed observ- 
ation, the external mechanical factors involved in the movements 
of the gastropod foot. 
The observations recorded in this paper were made partly at 
the Bermuda Biological Laboratory, at the Harvard Zodlogical 
Laboratory, and at the Biological Laboratory of the United States 
Bureau of Fisheries at Woods Hole. I am under obligations to 
the directors of the laboratories mentioned for the materials and 
opportunities for carrying on these studies. 
TYPES OF MOVEMENT 
When the locomotor movements of the foot in many species of 
gastropods are compared, a surprising diversity is found. These 
different types of movement have been well classified by Vlés 
