NOVEMBEB 25, 1910] 



SCIENCE 



731 



were consistent with it. We are apt to for- 

 get, nowadays, that there is no a priori 

 reason for regarding the resemblances and 

 diiferenees that we observe in organic 

 forms as something different in kind from 

 the analogous series of resemblances and 

 differences that obtain in inanimate ob- 

 jects. This was clearly pointed out by 

 Fleeming Jenkin in a very able and much- 

 referred to article in the North British Re- 

 view for June, 1867, and his argument 

 from the a priori standpoint has as much 

 force to-day as when it was written forty- 

 three years ago. But it has lost almost all 

 its force through the arguments a posteri- 

 ori supplied by morphological science. 

 Our belief in the transmutation of animal 

 organization in past time is founded very 

 largely upon our minute and intimate 

 knowledge of the manifold relations of 

 structural form that obtain among adult 

 animals; on our precise knowledge of the 

 steps by which these adult relations are 

 established during the development of dif- 

 ferent kinds of animals; on our constantly 

 increasing knowledge of the succession of 

 animal forms in past time; and, generally, 

 on the conviction that all the diverse 

 forms of tissues, organs and entire ani- 

 mals are but the expression of an infinite 

 number of variations of a single theme, 

 that theme being cell-division, multiplica- 

 tion and differentiation. This conviction 

 grew but slowly in men's minds. It was 

 opposed to the cherished beliefs of cen- 

 turies, and morphologj' rendered a neces- 

 sary service when it spent aU those years 

 which have been described as "years in the 

 wilderness" in accumulating such a mass 

 of circiimstantial evidence in favor of an 

 evolutionary explanation of the order of 

 animate nature as to place the doctrine of 

 descent with modification on a secure foun- 

 dation of fact. I do not believe that this 

 foundation could have been so securely laid 



in any other way, and I hold that zool- 

 ogists were actuated by a sound instinct in 

 working so largely on morphological lines 

 for forty years after Darwin wrote. For 

 there was a large mass of fact and theory 

 to be remodelled and brought into harmony 

 with the new ideas, and a still larger vein 

 of undiscovered fact to explore. The mat- 

 ter was difficult and the pace could not be 

 forced. Morphology, therefore, deserves 

 the credit of having done well in the past : 

 the question remains, What can it do in 

 the future? 



It is evident, I think, that it can not do 

 much in the way of adding new truths and 

 general principles to zoological science, 

 nor even much more that is useful in the 

 verification of established principles, with- 

 out enlarging its scope and methods. 

 Hitherto — or, at any rate, until very re- 

 cently — it has accepted certain guiding 

 principles on faith, and, without inquiring 

 too closely into their validity, has occupied 

 itself with showing that, on the assump- 

 tion that these principles are true, the 

 phenomena of animal structure, develop- 

 ment and succession receive a reasonable 

 explanation. 



We have seen that the fundamental prin- 

 ciples relied upon during the last fifty 

 years have been inheritance and variation. 

 In every inference drawn from the com- 

 parison of one kind of animal structure 

 with another, the morphologist founds him- 

 self on the assumption that different de- 

 grees of similitude correspond more or less 

 closely to degrees of blood-relationsliip, 

 and to-day there are probably few persons 

 who doubt that this assumption is valid. 

 But we must not forget that, before the 

 publication of the "Origin of Species," 

 it was rejected by the most influential 

 zoologists as an idle speculation, and that 

 it is imperilled by ilendelian experiments 

 showing that characters may be split up 



