54 BIOLOGICAL SOCIETY OF WASHINGTON. 



Through the operation of these two principles the phenomena 

 of adaptation are explained. Adaptation is placed by him in 

 what seems to be a new light, as the tendency of the organism 

 to respond through modification of form and structure to an 

 ever-changing environment. The introduction of this form of 

 words by Mr. Spencer has been of the utmost value to science 

 in affording it a clear and precise terminology for the most 

 important of all phenomena. Lamarck floundered about in 

 straining after such a terminology. As I have shown he gen 

 erally used the word circumstances for Spencer's environment, 

 but in many cases he employed the word medium {milieu} 

 and he occasionally approached the Spencerian expression so 

 nearly as to speak of the environing medium (milieu environ- 

 nanf)* His idea was undoubtedly the same, but he lacked 

 both the literary training and the philosophic power to present 

 it in its best light. 



Mr. Spencer showed that the general proposition that the 

 organism must be permanently, constantly, and profoundly 

 influenced by the environment is one that cannot be logically 

 escaped. It is not a mere a priori deduction, but rests upon 

 all the facts and phenomena of the organic world which he 

 marshaled in a most masterly manner in its support. But 

 the Neo-Darwinians who deny this because it conflicts with 

 their new hypothesis, never cease to demand facts. Haeckel's 

 reply to this was eminently just, that this new hypothesis is 

 itself wholly unsupported by facts, in the sense in which they 

 use the term. It is an inference from the study of embryology, 

 and an opposite inference is as legitimate as the one they 

 draw. The truth is that the real phenomena of heredity are 

 too recondite for direct observation. We are dealing with the 



Philosophic Zoologique, Vol. II, pp. 5, 304. 



