RADIARIKS. 197 



of the ocean would make in their ranks. The 

 manner in which they are propagated has not 

 been ascertained, but from their infinite num- 

 bers in every sea, their progeny must be incon- 

 ceivable. 



Another phosphoric animal of the present 

 tribe is distinguished by a dorsal crest, resem- 

 bling a vesicle full of air, and which it is said to 

 use as a sail, like many of the Molluscans, to 

 conduct it over the surface of the waves. It is 

 connected with the body only by its middle, its 

 extremities being at liberty, which enables the 

 animal to steer its course in any direction. 



I shall mention one more of these gelatines, 

 which falls under the observation of every one 

 who is fond of sailing, or rowing, in a boat on 

 the ocean or in its estuaries. If he cast his eye 

 upon the water in fair weather, he will see num- 

 bers of animals, in shape resembling an expanded 

 umbrella, with some flesh-coloured organs round 

 the summit or centre, carried with the rising or 

 falling tide, and dancing along with a seemingly 

 undulating motion : these belong to what are 

 vulgarly called the jelly-fish, or sea-nettles. 1 

 Though the body of the animals of this tribe is 

 gelatinous and easily melts, yet its weight is 

 considerable, and it is said that they can render 

 themselves heavy or light at pleasure, which 

 some effect by means of a natatory vesicle, but 

 the means in all has not been ascertained ; unless 



1 PLATE III. FIG. 1. 



