LOCOMOTION IN GASTROPODS. 



A millimeter rule was fastened above the foot. Particles of 

 dry carmine were then dropped on the water and as they were 

 driven with the mucus down the foot by the active cilia, it was 

 possible to record their speed over a distance of 5 mm. with con- 

 siderable accuracy. 



For some time all attempts at securing the ciliary rate for 

 Alectrion obsoleta were unsuccessful. The snails either continued 

 in their efforts to right themselves or else failed to expand their 

 feet at the surface of the water, as Alectrion trivittata did with 

 little hesitancy. When about to abandon the experiment some 

 individuals not fully grown were tried, and their behavior was 

 so satisfactory the desired records were readily obtained. In 

 one instance continuous ciliary movement was watched for 

 about three quarters of an hour. It is quite possible that the 

 difficulty encountered with the older individuals was due to 

 the fact that in the adult state the species does not have the 

 habit of surface floating, whereas the younger animals adapted 

 themselves to the inverted position more readily because they 

 had more recently abandoned it under natural conditions. 



The results of the tests made upon Alectrion obsoleta are shown 

 in Table I. They indicate that the average locomotor rate is 

 practically identical with the rate at which carmine grains are 

 driven along the foot by the beating cilia. 



TABLE I. 



Alectrion obsoleta. 



Locomotor Rate. 

 (Rate at which Snails Moved a Distance of 5 Mm.). 



Ciliary Rate. 



(Rate at which Carmine 



Grains were Carried a 



Distance of 5 Mm. Over 



Ciliated Foot.) 



Animal number one proved to be a faster moving individual 

 than any of the others timed, and it will be noted that the average 

 ciliary rate is also fast. Considering the fact that the cilia 

 are subject to great variation in rapidity of movement, the corre- 

 spondence in rates is closer than might be expected, and to my 

 mind affords conclusive evidence that locomotion is entirely 

 dependent on the action of cilia. 



