14 TOILERS IN THE SEA. 



" Edward Forbes pointed out long ago the kind 

 of inverted analogy which exists between the distri- 

 bution of land animals and plants, and that of the 

 fauna and flora of the sea. In the case of the land, 

 while at the level of the sea there is, in temperate 

 and tropical regions, a luxuriant vegetation with a 

 correspondingly numerous fauna, as we ascend the 

 slope of a mountain range the conditions gradually 

 become more severe ; species after species belonging 

 to the more fortunate plains beneath disappear, and 

 are replaced by others whose representatives are 

 only to be found on other mountain ridges, or on 

 the shores of an arctic sea. In the ocean, on the 

 other hand, there is along the shore line, and within 

 the first few fathoms, a rich and varied flora and 

 fauna, which participates and sympathises in all the 

 circumstances of climate which affect the inhabitants 

 of the land. As we descend, the conditions gradu- 

 ally become more rigorous, the temperature falls, 

 and alterations of temperature are less felt. The 

 fauna becomes more uniform over a larger area, and 

 is manifestly one of which the shallower water fauna 

 of some colder region is to a great extent a lateral 

 extension. Going still deeper, the severity of the 

 cold increases, until we reach the vast undulating 

 plains and valleys at the bottom of the sea, with 

 their fauna partly peculiar and partly polar a region 

 the extension of whose extreme thermal conditions 



