LOW GRADES OF MARINE LIFE 93 



Although the animal forms of the deep are proportionall)' 

 far more diversified, and attain to relatively higher states of 

 life than the plants of that realm, they are also much inferior 

 to their relatix'es of the land. Each of the great ty[)es has its 

 representatives among the marine forms, and certain of them, 

 as for instance the group of animals commonly known as 

 radiates, to which the polyps and star-fishes belong, arc, with 

 some trifling exceptions of species which live in fresh water, 

 confined to the sea. But all the mammals, birds, and insects, 

 the groups which contain the intelligent animals, are essen- 

 tially the creations of the continents ; the few members of the 

 series which have developed close and permanent relations 

 with the ocean, such as the whales, penguins, and rare marine 

 insects, have clearly been derived from characteristic land 

 forms, which, in the rude struesrle for existence, have been 

 forced to resort for subsistence to the sea. The greater part 

 of the higher species avoid the sea, for it is to them a place 

 of death. 



Nothing is clearer than the fact that all our land animals 

 have been derived from parent stocks which had their origin 

 in the waters ; it is not so certain as to plants, but it is proba- 

 ble that they, too, were first nurtured in the sea. In the land 

 areas these great groups of animal and vegetable organisms 

 attain their perfection. The articulates and vertebrates are 

 at their best above the level of the waters, and in them alone 

 do we find intellectual species. How does it come about that 

 though the deep has been the cradle of these varied creatures 

 it has not been the place of their fuller development ? The 

 answer is plain, and in it we shall lind some most important 

 teaching. A common view of the action of natural selection 

 is, that, oriven a full measure cf increase and a fair share of 



