HYDROIDS AND JELLY-FISHES. 



darting about in it were but a part of the element in 

 which it floats (No. 25).* In shape it is like a tiny 

 cup turned upside down ; from the lower side hang 



four long threads ; in the centre of 

 the lower side hangs a proboscis, 

 at the end of which is the mouth, 

 and four tubes run from the sum- 

 mit of the upper side to the lower 

 edge, where a circular tube unites 

 them all around. It seems to de- 

 light in its life : it shoots through 

 the water in every direction, and 

 appears to move by breathing, for 

 every motion is made by a sud- 

 den contraction and expansion, 

 which is in truth produced by the 

 taking in and throwing out of 

 water under the cup. Up and 

 down, and on every side it darts 

 about ; and no bird can enjoy its 

 flight through the air more than 

 this animal which scarcely seems 

 to have a material body, so frail 

 and unsubstantial is it appears 

 to enjoy its freedom of motion 

 through the water. It is perfectly 

 transparent : a drop of water, a 

 bubble of air, a spider's web, a 

 fly's wing, any thing that has form and shape at all, can 

 hardly be more slight in texture than this little creature. 

 And this is the being produced from the cluster of ani- 



No. 25: Sarsia. 



No. 25. 



