194 Mr. W. Bateaon. Heredity, Differentiation, 



generally. The conception of heredity is tlms greatly simplified, and 

 that phenomenon is seen in its true relation to the other phenomena of 

 life, becoming merely a special case of the phenomenon of Division and 

 repetition of parts. 



This idea came first to me as it has perhaps to others when I was 

 studying the phenomena of Variation in Meristic Series, and in writing 

 on that subject I introduced an outline of the conceptions involved.* 

 On that occasion I ventured to carry this reasoning a step further, as 

 it seemed, and to suggest that the resemblance which we call Heredity may 

 be a special cute of fit? phenomenon of Symmetry. The thought then 

 expressed has been a constant companion ever since, and I have 

 become more and more convinced that it is fundamentally true. 



I should welcome Professor Pearson's paper inasmuch as it is an 

 attempt the only one, so far as I know to emphasise and develop 

 this conception ; for, like him, I am sure that it may provide the key 

 to the nature of heredity, perhaps also to problems beyond. 



Variation in some of its essential features may thus perhaps be 

 reduced to a geometrical problem. One of the many factors or con- 

 ditions of fraternal resemblance may be Symmetry of division, quanti- 

 tative and qualitative. The reference to the phenomenon of Sym- 

 metry seemed to me to carry the principle a stage further, and to 

 show Heredity as a special case of a phenomenon, the conditions of 

 which we may reasonably hope, in a measure, to apprehend in at least 

 its simpler phases. Professor Pearson, on the contrary, avoids mention 

 of Symmetry. This arises, I presume, from a desire to use a more 

 general expression, and from a reluctance to appear to exclude from 

 his comparison the relation between members of Linear or Successive 

 Series, whose mutual relationship is not one of Symmetry in the 

 ordinary sense. He would probably prefer to regard Symmetrical 

 division as a phase or perhaps as a consequence of the phenomenon of 

 the production of " undifferentiated like parts " occurring under special 

 conditions. 



I still think something is gained by inverting the statement and 

 speaking of the likeness between the parts as a phenomenon of Sym- 

 metry. In some respects Professor Pearson's mode of expression is 

 preferable as being more comprehensive, but mine has the advantage 

 of keeping before the mind the fact that it is in the Symmetry of c.ell- 

 tlivision that the resemblance between relatives is presented in its 

 simplest form ; and also that the axes along which the " like parts " 

 are produced are frequently definite. 



Thus, fraternal correlation in its most striking manifestation is seen 

 in the simultaneous variations of Homologous Twins. t 



* For a somewhat fuller treatment see ' Materials for the Study of Variation,' 

 181)4, lutrod. Sect, VII; and also p. 21. 



f See ' Materials,' pp. 559 and 560. Following the work of Driesch and others 



