Vol. 3] 



Bovarcl. — Conchjlostoma patens. 



353 



closely applied to the bottom than any other part, giving the 

 appearance of dragging". 



There is some difference between gliding on the bottom and 

 on the surface film. In the first case, the entire body is in close 

 relation to the substratum : in the second, only a small part act- 

 ually comes in contact with the film (figs. 5 and 6). In this case, 

 only the adoral zone touches the film and the rest of the body 

 sinks away, suggesting that the body was so heavy that it could 



5. 



Fig. •'5. — An animal gliding on the surface film. 



Fig. 6. — The shaded portion is that which is in actual contact ^vith the 

 surface film. 



not hold itself in a horizontal position on the film. The right and 

 left lips are close to the surface, while the dorsal part of the adoral 

 zone is well arched to form as large a funnel as possible. In 

 movement on the surface film the spreading of the lips which ap- 

 pears in gliding on the bottom is absent. Practically all the cilia 

 enter into this movement, those of the dorsal surface beat as well 

 as those of the ventral surface. The ciliary action shows waves 

 of contraction. These appear to run just in the opposite direc- 

 tion to the beat of the cilia, so that this forms a means of deter- 

 mining the direction of the beat of the cilia. Concerning the 

 action of the cilia during" this movement it is sufficient to say 

 that all are concerned, those of the dorsal surface beat forwards 

 and reverse at the same time as those on the remainder of the 



