MEMOIR* OF JAMES D. DANA. 465 



them — a beauty which has so affected the imagination of artists as to have 

 given rise to a peculiar South Sea literature which reads like fairy litera- 

 ture ; it is of equal or even greater scientific interest because of the infinite 

 variety of life-forms crowded together on the reefs, making them a ver- 

 itable zoological garden, the greatest gathering-ground of the naturalist 

 and the greatest theater of the struggle for life to be found anywhere on 

 earth. But more than all to the geologist are they of deepest ii"yDerest on 

 account of the evidence they afford of movements of the crust of the 

 earth on a scale of grandeur commensurate with the formation of those 

 greatest features of the earth-surface, continental areas and oceanic basins. 

 The subsidence theory of atolls and barriers powerfully affected the mind 

 of Dana, and, although it originated with Darwin, no one, not even Dar- 

 win himself, has done more by close observation and wide generalization 

 to establish it on a solid foundation. It is true that as a universal theory, 

 at least for barriers, it can no longer be maintained, having been dis- 

 proved by the observations of Agassiz on the coast of Florida, but as a 

 general theory, on which may be based the conclusions drawn from it 

 by Darwin and Dana, that the floor of the mid-Pacific over an enormous 

 area is sinking and has been sinking for ages, I believe it still holds its 

 own as by far the most probable theory. Correlative with this sinking 

 is the rising of the American continents, especially on their western side. 

 The second line of thought suggested by the observations of his famous 

 voyage, but which he continued to follow up during his whole life, was 

 the idea of cephalization or headward development ; that is, the increas- 

 ing dominance of head functions over other functions, and therefore the 

 increasing subordination of the whole structure of the animal body to 

 the service of the head as we go up the scale in any class. Dana an- 

 nounced this as a law of structural elevation in any class, or, as we would 

 say now, as a law of evolution, and therefore as a guide to classification. 

 He came upon this law in studying the modifications of the limbs of 

 crustaceans. He found that as we rise in the scale more and more of 

 the appendages are released from the function of locomotion to be de- 

 voted to the service of the head. He afterwards applied it to other 

 classes of animals. Like all great thoughts, its fertility is inexhaustible 

 and its application boundless. It might be generalized as a gradually 

 increasing dominance of the higher over the lower and of the highest 

 over all. In this form the law is universal. To give one illustration of 

 my own: In passing from the lowest protozoan to man, among the many 

 systems of organs which are successively differentiated there is an in- 

 creasing dominance of the highest system, namely, the nervous system. 

 Then in the nervous system an increasing dominance of the highest part, 

 that is the brain. In the brain an increasing dominance of the highest 



