OCEAN ANIMALS: SPONGES, SEA-ANEMONES, ETC. 133 



specimens have been dredged up from depths of a mile 

 below the surface. They range in size from " umbrellas " 

 or disks a few millimeters in diameter to disks of a diam- 

 eter of two meters (2^ yards). They are all carnivorous, 

 preying on other small ocean animals, which they catch by 

 means of their tentacles, provided with stinging-threads. 

 The tentacles of some of the largest jellyfishes ' ' reach 

 the astonishing length of 40 meters, or about 130 feet." 

 Many of the jellyfishes are beautifully colored, although 

 all are nearly transparent. Almost all of them are phos- 

 phorescent, and when irritated some emit a very strong 

 light. 



The so-called " colonial jellyfishes " are floating or 

 swimming colonies of jellyfishes and polyps composed of 

 many individuals closely joined. These individuals are 

 all of one species, but are of different forms or kinds, 

 each kind having a special function to perform in the life 

 of the colony. For example, some individuals catch all 

 the food for the colony ; some make the motions ; some 

 are especially sensitive to the presence of enemies or prey, 

 and some produce all the young. These various individ- 

 uals act like the separate organs of our own body. The 

 beautiful Portuguese "man-of-war" (fig. 95) is one of 

 these colonial jellyfishes. It appears as a delicate bladder- 

 like float, brilliant blue or orange in color, usually about six 

 inches long, and bearing on its upper surface, which pro- 

 jects above the water, a raised parti-colored crest, and on 

 its under surface a tangle of various appendages, thread- 

 like, with grape-like clusters of little bell- or pear-shaped 

 bodies. Each of these parts is a specially modified indi- 

 vidual, produced by budding from an original central 

 polyp. The Portuguese man-of-war is very common in 

 tropical oceans, and sometimes vast numbers swimming 

 together make the surface look like a splendid flower- 

 garden. 



