CILIARY AND MUSCULAR LOCOMOTION IN THE 

 GASTROPOD GENUS POLINICES. 



MANTON COPELAND, 

 SEARLES BIOLOGICAL LABORATORY, BOWDOIN COLLEGE. 



INTRODUCTION. 



Although gastropod locomotion has often been made a subject 

 of investigation by naturalists and physiologists with the result that 

 the characteristic muscular form of progression is now fairly well 

 understood, it appears that little is known concerning the peculiar 

 and equally interesting activities of cilia which occur on the feet 

 of numerous species of snails, and the part they may play in loco- 

 motion, notwithstanding the fact that Quatrefages as early as 1843 

 believed them to be locomotor in function. A study of pedal cilia 

 in two species of marine gastropods belonging to the genus Alcc- 

 trion led me to conclude not only that locomotion was due to ciliary 

 action, but also that this action, unlike that of ordinary cilia, was 

 eithp" directly or indirectly under the control of the nervous system 

 (Copeland, '19). Recently similar studies on the genus Polinices 

 have been carried on at the Marine Biological Laboratory at Woods 

 Hole, the results of which are here recorded. This group appears 

 to contain the largest animals which have been reported as exhibit- 

 ing ciliary locomotion. The snails also have a muscular form of 

 progression, thus showing a combination of locomotor methods 

 which I believe has not been described for marine gastropods. 



Most of the work has been done on Polinices (Neverita) dupli- 

 cata (Say), although the more northern species Polinices (Euspira) 

 hcros (Say), which is closely similar to the preceding, has been 

 studied to some extent. Unless otherwise specified, observations 

 here noted refer to the former species. 



The large foot of Polinices is differentiated anteriorly into a 

 well-developed propodium which is prolonged over the head region 

 and a part of the shell. This organ, bluntly pointed at the anterior 

 end, is capable of great extension and freedom of movement, and 

 when protruded bears a striking resemblance to the mammalian 



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