April — sept. 1858.] Order Radiata. 127 



ping swimming cavity which is generally shaped like a hollow bell, 

 and is provided with an opening which is actively opened and shut: 

 and the water streaming out of the swimming-bell drives the ani- 

 mal forward by its rebound. Under the covering piece there is a 

 worm-like sucking body which in its extension shows a mouth of 

 angular radiated form, at the base of which are hidden uncommon- 

 ly long seizing and stinging threads. 



It is still a question whether these animals, which principally 

 form the genus Diphyes, are not detached pieces of one composite 

 animal ; for there are cases, where such creatures are these, are 

 found in the sea to the number of forty or more, attached to one 

 common stalk, "at the upper end of which are two large swimming- 

 bladders, each of which seems to contain an oil pustule : — see fig. 6, 

 plate v. Each single animal can move independently, but the ex- 

 tremely contractile stem has also a proper motion, and the whole 

 is drawn hither and thither through the water by the two large 

 swimming bladders with great ease. The stem is hollow, and the 

 nourishing fluid from the different animals circulates in its tube. 



In other genera, for example Stephanomia, the union of the sin- 

 gle animals is still more intimate. The swimming-bells are placed 

 sometimes in rows, but more generally irregularly at the fore-end 

 of the stalk, which contains an air-bladder. On the stalk itself 

 are countless worm-like sucking apertures, each surrounded by a 

 quantity of seizing and stinging threads. There is no more extra- 

 ordinary spectacle than such a creature which swims in the sea 

 with all its organs extended, like a transparent reddish plume of 

 feathers about a span long, but when caught or touched the stalk 

 draws up with an elastic impulse, and it transforms itself into a 

 shapeless lump of jelly so that the tyro sorrowfully throws away 

 his unfortunate prize. Is it a simple animal with swimming bells 

 and sucking tubes, or a Polyp-stock adapted for swimming with 

 various animals thrown swimming and eating ? Further enquiries 

 must give the answer to this question. Physophora ; Diphyes ; 

 Ersaca ; R7iizop7iysa ; Agahna ; Ilippopodius. 



Order Mollusca. — The extremely numerous kingdom of the 

 Mollusca is made up of such very different animals, that it is scarce- 



