386 



SCIENCE 



[N. S. Vol. XXVIII. No. 717 



tions of living things. It can not be de- 

 nied that the ontogenetic rhj^hm has the 

 two qualities observable in habit— namely, 

 a certain degree of fixity or automaticity, 

 and also a certain variability. A habit is 

 not irrevocably fixed, but may be altered 

 in various ways. Parts of it may be for- 

 gotten or new links may be added to it. 

 In ontogeny the fixity is especially observ- 

 able in the earlier, the variability in the 

 later, stages. Mr. Darwin has pointed out 

 that "on the view that species are only 

 strongly marked and fixed varieties, we 

 might expect often to find them still con- 

 tinuing to vary in those parts of their 

 striicture which have varied within a 

 moderately recent period." These re- 

 marks are in explanation of the "notor- 

 ious" fact that specific are more variable 

 than generic characters — a fact for which 

 it is "almost superfluous to adduce evi- 

 dence."^ This, again, is what we find in 

 habit: take the case of a man who, from 

 his youth up, has daily repeated a certain 

 form of words. If in middle life an addi- 

 tion is made to the formula, he will fiind 

 the recently acquired part more liable to 

 vary than the rest. 



Again, there is the wonderful fact that, 

 as the ovum develops into the perfect or- 

 ganism, it passes through a series of 

 changes which are believed to represent 

 the successive forms through which its an- 

 cestors passed in the process of evolution. 

 This is precisely pai-alleled by our own 

 experience of memory, for it often 

 happens that we can not reproduce the last 

 learned verse of a poem without repeating 

 the earlier part ; each verse is suggested by 

 the previous one and acts as a stimulus for 

 the next. The blurred and imperfect 

 character of the ontogenetic version of the 

 phylogenetic series may at least remind us 

 of the tendency to abbreviate by omission 

 what we have learned by heart. 



* " Origin of Species," 6th edition, p. 122. 



In all bi-sexual organisms the ontogen- 

 etic rhythm of the offspring is a combina- 

 tion of the rhythms of its parents. This 

 may or may not be visible in the offspring ; 

 thus in the crossing of two varieties the 

 mongrel assumes the character of the pre- 

 potent parent. Or the offspring may show 

 a blend of both parental characters. Se- 

 mon- uses as a model the two versions of 

 Goethe's poem — 



Ueber alien Gipfeln, ist Ruh, in alien Waldern, 



horest du, keinen Haueh. 

 Ueber alien Gipfeln, ist Huh, in alien Wipfeln, 



spiirest du, kaum einen Hauch. 



One of these terminations will generally 

 be prepotent, probably the one that was 

 heard first or heard most often. But the 

 cause of such prepotency may be as ob- 

 scure as the corresponding occurrence in 

 the formation of mongrels. We can only 

 say that in some persons the word "alien" 

 releases the word "Waldern," while in 

 others it leads up to "Wipfeln." Again, 

 a mixture of the terminations may occur 

 leading to such a mongrel form as: "in 

 alien Waldern horest du kaum einen 

 Hauch." The same thing is true of 

 music; a man with an imperfect memory 

 easily interpolates in a melody a bar that 

 belongs elsewhere. In the ease of memory 

 the introduction of a link from one mental 

 rhythm into another can only occur when 

 the two series are closely similar, and this 

 may remind us of the difficulty of making 

 a cross between distantly related forms. 



Enough has been said to show that there 

 is a resemblance between the two rhythms 

 of development and of memory; and that 

 there is at least a prima facie ease for be- 

 lieving them to be essentially similar. It 

 will be seen that my view is the same as 

 that of Hering, which is generally de- 

 scribed as the identification of memory 



= "Die jSIneme," 2d edition, pp. 147, 221, 303, 

 3-15. 



