16 SEAWEEDS 
size of the sun in the early stages of the earth’s his- 
tory—an idea first introduced into geological specu- 
lations by Blandet (Bull. Soc. Géol. de France, sér. 2 
t. 25, p. 777, 1867-68),. who likewise discussed the 
relations of Arctic and Antarctic faunas—together 
with the greater amount of aqueous vapour in the 
atmosphere and the greater mass of the atmosphere.” 
(Murray, in Summary of Results, “Challenger” Reports, 
1895.) 
Another interesting point in the distribution of 
seaweeds bearing on this subject is that those 
having an incrustation of carbonate of lime occur 
much more plentifully in the warmer oceans—a fact 
equally true of the marine animals, though the pro- 
cess of deposition is different. This very slight 
development of carbonate of lime structures in the 
cold waters of the polar regions is instructive when 
compared with the massive coral reefs constructed 
in the polar regions in Paleozoic and later geological 
times. 
It is a commonplace of biological knowledge that 
the nutrition of the animal kingdom is dependent 
upon the action of green vegetation in performing 
the primary office of converting the inorganic into 
the organic, and thus producing fitting substances 
for food. A casual observation of the great mass of 
terrestrial vegetation, and a comparison of it bulk for 
bulk with the animal life of the land, enables us to 
recognise the adequacy of the one asa balance to the 
other. On turning to the conditions that prevail in 
the ocean, it is at once apparent that a mere fringe of 
coast vegetation, extending to no great depth, can- 
