38 INTRODUCTION 



disappears, without giving evidence of its nature in dust or 

 gases, its body seeming to be a machine which transmutes, but 

 does not hold, the substances on which it grows. 



AlgaB, as has been said above, grow in definite zones, and each 

 zone has also a definite animal life which finds there its food. 

 Darwin says : u In all parts of the world a rocky and partially 

 protected shore perhaps supports in a given space a greater 

 number of individual animals than any other station." And 

 speaking of the Laminariacece, he adds : " I can only compare 

 these great aquatic forests of the southern hemisphere with the 

 terrestrial ones in the intertropical regions. Yet if in any 

 country a forest was destroyed I do not believe nearly so many 

 species of animals would perish as would here from the destruc- 

 tion of the kelp." The same may be said of the Sargasso Sea, 

 where millions of living creatures make their home. In every 

 kind of marine fauna there are species which derive, if not the 

 whole, at least a part of their nourishment from the seaweeds. 



The vegetation in the narrow boundary of the three zones is 

 palpably inadequate to supply the needs of the animal life which 

 exists in deeper waters. But over the broad area of the ocean 

 there exists a vast number of pelagic, free-floating algae, which, 

 although microscopical in size, are almost infinite in numbers. 

 In illustration of this it has been estimated that, although they 

 are not especially numerous in the Sargasso Sea, yet if all the 

 seaweed there were gathered into one mass and the free-floating 

 algae into another, the bulk of the latter would exceed that of the 

 former. The pelagic flora consists of Diatomacece, Protococcacece, 

 PendiniecB, and others. Undoubtedly it is on these pastures that 

 fishes feed, as well as other organisms which in turn are food for 

 fishes. 



Fticus and Laminaria constitute the kelp from which iodine is 

 obtained, and were at one time the source of the potash of com- 

 merce. Fucus vesiculosus is a constituent of a medicine used as a 

 cure for obesity. Chondrus crispus, commonly known as Irish 

 moss, was a few years ago generally used as an article of diet. 

 Porphyra vulgaris (laver) is used by the Chinese for soups. Rho- 

 dymenia palmata (dulse) is an article of food in Ireland and Scot- 



