730 



SCIENCE 



[N. S. Vol. XXXII. No. 830 



What remains for morphology to do in the 

 future ? 



To begin with, then, what do we include 

 under the term morphology? I must, first 

 of all, protest against the frequent assump- 

 tion that we are bound by the definitions of 

 C. F. Wolff or Goethe, or even of Haeekel, 

 and that we may not enlarge the limits of 

 morphological study beyond those laid 

 do^m by the fathers of this branch of our 

 science. We are not — at all events we 

 should not be — bound by authority, and 

 we owe no allegiance other than what rea- 

 son commends to causes and principles 

 enunciated by our predecessors, however 

 eminent they may have been. 



The term morphology, stripped of all 

 the theoretical conceptions that have 

 clustered around it, means nothing more 

 than the study of form, and it is applicable 

 to all branches of zoology in which the re- 

 lationships of animals are determined by 

 reference to their form and structure. 

 Morphology, therefore, extends its sway 

 not only over the comparative anatomy of 

 adult and recent animals, but also over 

 paleontology, comparative embryology, 

 systematic zoology and cytology, for all 

 these branches of our science are occupied 

 with the study of form. And in treating 

 of form they have all, since the acceptance 

 of the doctrine of descent with modifica- 

 tion, made use of the same guiding prin- 

 ciple — namely, that likeness of form is the 

 index to blood-relationship. It was the in- 

 troduction of this principle that revolu- 

 tionized the methods of morphology fifty 

 years ago, and stimulated that vast output 

 of morphological work which some persons, 

 erroneously as I think, regard as a depar- 

 ture from the line of progress indicated by 

 Darwin. 



We may now ask, what has morphology 

 done for the advancement of zoological sci- 

 ence since the publication of the "Origin 



of Species ' ' ? We need not stop to inquire 

 what facts it has accumulated: it is suffi- 

 ciently obvious that it has added enorm- 

 ously to our stock of concrete knowledge. 

 We have rather to ask what great general 

 principles has it established on so secure a 

 basis that they meet with universal ac- 

 ceptance at the hands of competent zool- 

 ogists 1 



It has doubtless been the object of mor- 

 phology during the past half -century to il- 

 lustrate and confirm the Darwinian theory. 

 How far has it been successful ? To answer 

 this question we have to be sure of what 

 we mean when we speak of the Darwinian 

 theory. I think that we mean at least two 

 things. (1) That the assemblage of ani- 

 mal forms as we now see them, with all 

 their diversities of form, habit and struc- 

 ture, is directly descended from a precedent 

 and somewhat different assemblage, and 

 these in turn from a precedent and more 

 different assemblage, and so on down to 

 remote periods of geological time. Further, 

 that throughout all these periods inheri- 

 tance combined with changeability of struc- 

 ture have been the factors operative in 

 producing the differences between the suc- 

 cessive assemblages. (2) That the modifi- 

 cations of form which this theory of evolu- 

 tion implies have been rejected or 

 preserved and accumulated by the action 

 of natural selection. 



As regards the first of these proposi- 

 tions, I think there can be no doubt that 

 morphology has done great service in es- 

 tablishing our belief on a secure basis. 

 The transmutation of animal forms in past 

 time can not be proved directly; it can 

 only be shown that, as a theory, it has a 

 much higher degree of probability than 

 any other that can be brought forward, 

 and in order to establish the highest pos- 

 sible degree of probability, it was neces- 

 sary to demonstrate that all anatomical, 

 embryological and paleontologieal facts 



