THE VERTEBRATES AND THEIR ENVIRONMENT 33 



animals and not plants, although they are so like them in form and 

 color. At Nassau, in the Bahama Islands, the visitor is taken in 

 a small boat, with windows of plate glass set in the bottom, to 

 visit the " sea-gardens " at the inner end of a channel through 

 which the pure water from the open sea flows between two coral 

 islands into the lagoon. Here the true reef corals grow in quiet 

 water, where they may be visited and examined. 



When illuminated by the vertical sun of the tropics and by the 

 light which is reflected back from the white bottom, the pure, 

 transparent water is as clear as air, and the smallest object forty 

 or fifty feet down is distinctly visible through the glass bottom of 

 the boat. 



As this ghdes over the great mushroom-shaped coral domes 

 which arch up from the depths, the dark grottoes between them 

 and the caves under their overhanging tops are lighted up by the 

 sun, far down among the anthozoa or flower animals and the 

 zoophytes or animal plants, which are seen through the waving 

 thicket of brown and purple sea-fans and sea-feathers as they 

 toss before the swell from the open ocean. ^ 



It appears, however, that what seem to be plants attached to 

 the bottom are in reality attached animals feeding upon other 

 animals that swim freely in the water. In these sea gardens the 

 bottom is like one vast mouth, or rather it is carpeted with innum- 

 erable mouths. Even further examination seems to show that 

 the animal life of the ocean possesses no visible means of support, 

 unless one examines the open water with the aid of a microscope. 

 In this way one discovers that in the ocean, as well as on land, 

 the green plant is the primary source of food supply. In the ocean, 

 however, the green plants consist of microscopic forms. Although 

 the number of species is relatively small, such an enormous number 

 of individuals are present in all the oceans that these organisms 

 furnish an abundance of food for the teeming animal population. 

 The inter-relationships whereby the material from this primary 

 source becomes available for larger animals are no more comph- 

 cated than those by which a sunilar elaboration of the food supply is 

 effected upon the land, beginning with the green plants and ending 

 with the largest carnivorous animals. A similar condition exists 

 in the life of inland waters (cf. Fig. 305, p. 550), although the 

 amount and importance of the larger aquatic vegetation is relatively 

 much greater than in the ocean. The conditions that have been 

 described for land, ocean, and fresh water, constitute a fundamental 



2 Brooks, W. K., "Foundations of Zoology," pp. 220--21. 



