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The Nautilus. 



Vol. XXII. OCTOBER, 1908. No. 6. 



SOME NOTES ON THE LOCOMOTIVE DISK OF STYLOMMATOPHORA. 



BY V. STERKI. 



During 1907 I made some studies and observations on the mor- 

 phology of some of our land snails, and especially on the foot. The 

 results were very incomplete and fragmentary ; but the notes re- 

 specting the sole and " locomotive disk " appear to be of some inter- 

 est, and a summary of them is here given. 



Of about thirty-seven species, I had occasion to observe living 

 animals, and of some of them preserved specimens could be com- 

 pared. The results obtained are somewhat at variance with those 

 published by other conchologists, which appear to have been ob- 

 tained mainly from preserved material. 



It may be mentioned that a piece of thin glass is conveniently 

 used to let the snails creep on. In this way, the sole can not only 

 be seen with the naked eye, but lenses and even strong doublets can 

 be used, and the foot seen in both reflected and transmitted light. 

 If kept on a slide, upside down, minute snails can be examined and 

 observed under a low-power microscope. It is recommended to 

 fasten a few small slips or narrow strips of glass on the glass plate, 

 best a pair of them close together, in order to observe the shape and 

 motions of the sole when detached from the even surface, while a 

 snail creeps over these obstacles. 



The majority of the snails show^ed locomotive waves on the under 

 surface of the foot while creeping. On about one-third, none could 

 be seen. The waves proceed from the posterior end, or from near 



