LIFE OF JAMES DWIGHT DANA 



contributor to the North American Review -, circumstances 

 that gave him influence with Mr. Webster, Mr. Everett, 

 and other public men of Massachusetts, whose support it 

 was important to enlist. The correspondence of the two 

 naturalists respecting the vexatious delays and interfer- 

 ences on the part of the authorities in Washington was 

 prolonged, though it does not seem worth while to 

 repeat in these pages the details of a controversy which 

 has long since passed out of mind. 



After Darwin's Origin of Species appeared, Gray was 

 engaged in the confidential exchange of opinions with 

 Dana. Until his last days he was a constant and highly 

 valued contributor to the Journal of Science. Some of 

 Gray's letters have appeared in the volume of correspond- 

 ence edited by his wife; but their reproduction here will 

 serve to throw light on the acceptance and modification 

 of Darwin's views. Dana's letters on these points will be 

 fully given. 



DANA TO ASA GRAY 



Analogies of Plant Life and Animal Life 



"NEW HAVEN, February 17, 1848. 



I am always glad of your criticisms, as I seek only 

 truth, and I feel the more attached to one who will help 

 me to avoid error. In this case I think you do not fully 

 understand me. I do not mean to imply that there is an 

 identity of forces in kind and action in the animate and 

 inanimate kingdoms. This is far from my belief; I 

 merely state that a common law as regards the force 

 operates in both kingdoms. This is the law of interval 

 or size, that is, that successive reproductions are separated 

 by intervals, usually regular (circumstances the same); 

 these intervals are intervals of comparative rest and 

 gradual growth, and are often intervals in size as well as 

 time. A length of interval may, therefore, be a fixed 

 quantity (cet. par.). For example, a certain size is neces- 

 sary for the production of a bud, and a certain interval of 



294 



