536 Animal Biology 



Fossil sponges, similar to present-day forms, have been found chiefly in 

 chalk and flint formations from the Cambrian period (550 million years 

 ago) to the present. 



The glass fibers of the glass sponges (Fig. 85) were formerly used in 

 making ''glass wool" which was used for filtering clumps of bacteria and 

 in the manufacture of toys and ornaments. This type of wool is now 

 made by melting glass and forcing it through small pores and rapidly 

 cooling the fine fibers. 



The commercial uses of sponges are too well known to require much 

 elaboration. The annual value of the sponge industry is approximated 

 at $2,000,000, while that of Florida alone approximates $700,000. Ro- 

 man soldiers were said to have used sponges as drinking utensils many 

 years ago. 



The United States Department of Agriculture states that sponge spic- 

 ules in the marsh soils of Florida wear away the shoes of men and the 

 hoofs of animals in a short time in the attempts to reclaim such lands. 



PHYLUM 3— COELENTERATA (HYDRA, CORALS, 

 SEA ANEMONE, SEA CUCUMBER) 



Hydra is slightly beneficial in that it captures mosquito larvae and 

 other insects, but it is detrimental in that it also captures Crustacea and 

 worms which might profitably have been used as food by higher animals. 

 Hydra has been observed actually to destroy young fishes in fish hatch- 

 eries. Hydra has been frequently used in experiments in grafting and 

 regeneration. 



Coelenterates, in general, are not commonly used as food by man but 

 are eagerly devoured by fishes (Figs. 88 to 95). Sea anemones are used 

 by Italians for food, in which case they are sold under the name of 

 "Ogliole" (Fig. 95). 



Coral reefs and islands may be formed by the limestone secretions of 

 innumerable corals (Fig. 96) which structurally somewhat resemble the 

 sea anemone. Such coral reefs may serve as protection or prove to be 

 treacherous hazards in ocean travel. The Great Barrier Reef extends 

 parallel to the northern coast of Queensland for over 1,000 miles and 

 at a distance varying from 10 to 100 miles from the shore. Many of the 

 islands of the Pacific are more or less of coral origin. Certain types of 

 corals are used in the manufacture of jewelry or for ornamental pur- 

 poses. The finest varieties of the rose pink coral cost about $500 per 

 ounce. Pale pink Japanese coral necklaces are frequently valued at 

 $5,000. 



