JELLY FISHES. 89 



about them that any attempt at their systematic arrange- 

 ment, and consequently their nomenclature, must be 

 considered as merely provisional. 



Suppose that we pick out a small and uninjured speci- 

 men, and bring it home for a closer examination. It 

 can be fairly seen in any basin filled with clear sea- 

 water ; but as some of its structures require the light to 

 pass among and through them before they can be distin- 

 guished, a glass vessel should be used if it can be 

 obtained. 



There are always several pastrycooks' shops at a sea- 

 side watering-place, and the proprietor Avill mostly lend 

 on hire to a customer one of the large cylindrical biscuit- 

 glasses. Bell glasses can mostly be obtained, but they 

 almost always have a greenish tinge, which destroys the 

 beauty of the Jelly Fishes placed in them. 



Here, then, is our jar of clear sea-water, and in it is a 

 Jelly Fish. 



The first point which will strike the observer will be 

 the pulsations of the disc. It continually expands and 

 contracts, as if it were the heart of some creature much 

 higher in the scale of nature. 



How and why does it pulsate ? 



As far as we know, one of the objects of the pulsation 

 is to allow as much water as possible to pass over the 

 various organs, much as a fish, by perpetually opening 

 and closing its mouth and gill-covers, impels the water 

 over the respiratory apparatus. At one time it was 

 thought that the pukation of the disc was intended to 



