THE MOVEMENTS OF SHORE ANIMALS i6i 



Turbellarian worms, e.g. the common Leptoplana 

 tremellaris, are remarkable for their flat shape, which enables 

 them to maintain the whole of the under surface of the 

 body in the closest contact with the substratum. Locomo- 

 tion is effected by the cilia of the ventral surface aided 

 probably by the longitudinal muscle layers of this surface 



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: iNCnES 



Fig. 12. — Successive positions occupied by pedal disc of a large 

 anemone {Metridium dianthus) on the glass of an aquarium tank during 

 a period of three and a half weeks. 



(Gamble, 1896), and results in a remarkably even flowing 

 motion which is very beautiful to watch. The term " pelli- 

 cule animee " or ** living film " often applied to these forms 

 is exceedingly apt. Turbellarians also utilise the surface 

 film of water, and are able to swim very gracefully. Both 

 of these methods of locomotion are dealt with under other 



M 



