PEDAL LOCOMOTION IN ACTINIANS 121 



selves with water and in 12 to 15 hours after the operation many 

 of them were creeping about precisely as the whole animals did. 

 A single record will illustrate this. One of the animals without 

 its oral disc began creeping and was observed to carry out 4 

 movements in 16.5 minutes traveling in that period 7 mm. An 

 animal with its oral disc intact that had been kept under similar 

 conditions as a control carried out 4 locomotor movements in 

 22.5 minutes, travelling in that period 6 mm. As the differences 

 between these two sets of records are no more than may be seen 

 in any pair of normal individuals, the locomotion of the two ani- 

 mals may be regarded as essentially identical. Individuals with- 

 out oral discs not only creep as whole individuals do, but they 

 also attach themselves to a glass surface as firmly as do those 

 with oral discs. Furthermore those without oral discs creep 

 away from the light as consistently as do normal individuals. 

 In fact, 'so far as the creeping is concerned, it is impossible to 

 distinguish one class from the other except perhaps that the 

 operated animals are somewhat less inclined to creep than the 

 normal ones are. 



The conclusion to be drawn from this experiment is that the 

 pedal disc and its immediately adjacent parts contain all the 

 neuromuscular mechanism that is necessary to creeping, in 

 other words, this function is in no sense dependent upon the as- 

 sumed nervous centers of the oral disc. These results are in 

 entire accord with Loeb's investigations ('95, p. 418; '99, p. 34) in 

 which he has shown that an Actinia equina from which the oral 

 end has been cut off will creep more or less continuously on glass, 

 and will attach itself firmly to a mussel shell just as a normal ani- 

 mal will. They are also in accord with Jordan's results ('08, '12) in 

 which he has shown that the reflex excitability and muscle tonus 

 of actinians is not under the control of superior nervous centers. 

 They are quite at variance with such views as those expressed by 

 Gosse ('60, p. 81), who in speaking of the creeping of Sagartia 

 pallida states that "it was impossible to witness the methodical 

 regularity of the process and the fitness of the mode for attaining 

 the end, without being assured of the existence of both conscious- 

 ness and will in this low animal form." In this respect the 



