DIFFERENT WAYS OF SWIMMING 



a cloud. In this case, the propeller is a short pipe, the 

 " funnel " justly so-called, wider at its base than at 

 its point where it opens outwards, while its base 

 communicates with the cavity left between the bag-like 

 cloak and the body. In the normal state, this space is 

 filled with water which comes in through the wide 

 opening and bathes the gills by which the cuttlefish 

 breathes. When it takes to flight, it closes this entrance 

 and so imprisons the water it contains; then, the cloak 

 contracting vigorously, this water is expelled through 

 the funnel, the only way in which it can escape, and, 

 violently forced out by this means, produces a swift 

 recoiling motion which drives the body briskly back- 

 wards. This extraordinary method, which is unknown 

 in fishes, is also that of the poulps when swimming, 

 and of the arrow-like squids which, living in the open 

 sea, regularly and continually move in this way. 



This examination of the other inhabitants of the 

 tank shows us new and unexpected aspects. It 

 accentuates the impression of diversity which the fish, 

 considered by themselves, had caused; this increases 

 when it is extended to other creatures. Occasionally, 

 we have an opportunity to fish up the bell-shaped 

 jelly-fish and watch their method of swimming; their 

 progress, which is not very rapid, is practically limited 

 to keeping themselves up, but there is, besides, a 

 definite move forward, effected by sudden contractions 

 of the circumference of the bell. Then again, we may 

 see the beautiful Ctenophores, whirling about like 

 massive or striped ribbon-like jelly-fish, made of a 

 transparent or very slightly rose-tinted glassy sub- 

 stance. These creatures swim by beating the water 

 with little flappers like the teeth of a comb, set out 

 along the body in eight radiating bands. Among the 

 inert shell-fish lying on the bottom, we may even see 

 some of them, like the little scallops or pectens, 

 suddenly get up, perform a series of little leaps, 

 beating the water with the two valves of the shell, 



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