NATURE'S JEWELS. 171 



with admittedly animal bodies, and that these im- 

 mensely preponderate over their animal or semi- 

 animal attributes. Thus, the Diatoms evolve oxy- 

 gen, rise to the surface of the water in sunlight, 

 and in the Antarctic Ocean (as we are informed 

 by Dr. Hooker) their vegetable nature is of such 

 importance that but for them the water, in the 

 utter absence of other vegetables, could not be 

 purified from the carbonic acid caused by animal 

 respiration and decomposition, and that thus by 

 their immense numbers they not only furnish 

 an abundance of vegetable food to the herbivor- 

 ous mollusca, and other inhabitants of the sea, 

 but that without them the balance of nature would 

 be so disturbed as to render the continuance of 

 animal life impossible in those regions. Yet they 

 exist in equal, or even in greater abundance, in 

 tropical seas. Dr. Wallich found them, with but 

 little interruption, to the depth of some feet 

 throughout six degrees of longitude in the Indian 

 Ocean, and there they were of such gigantic size as 

 even to be visible individually to the naked eye. 

 Thus the argument for their vegetable nature has 

 a twofold aspect ; for if vegetable, by analogy we 



