332 IN LOWER FLORIDA WILDS 



is pelagic, that is, it floats and swims either on or 

 comparatively near the surface and is carried about 

 in the sea without fixed abode. 



Besides those larger pelagic forms already 

 mentioned (Janthinas, the Physalia or Portuguese 

 man-of-war, the Vellelas and Porpitas) there are 

 hosts of smaller Medusae, and unnumbered mil- 

 lions of Pteropods, many of the latter having 

 exquisitely beautiful hyaline or glassy little shells. 

 Among -these pelagic moUusks are the Hyalzeas, 

 the Creseis, which look like silvery needles, and 

 the Cuvierias, whose tests resemble dainty little 

 chalices. There is an infinite variety of Proto- 

 zoans, and among them the Noctilucas which fur- 

 nish much of the phosphorescence of the sea. 

 The floating gulf weed {Sargassum nutans) bears a 

 wealth of life, especially small crustaceans and 

 moUusks. Many of these pelagic animals are 

 very short lived, but they reproduce marvelously. 

 According to Alexander Agassiz some of the 

 Copepods, which are minute crustaceans, have no 

 less than thirty generations in three weeks. 



These pelagic animals are constantly dying, and 

 it is aptly said there is always a gentle rain of food 

 falling over the bottom of the ocean. Besides 



