Aug., is 93 . RECAPITULATION THEORY IN BIOLOGY. 139 



is clearly an impossibility — any changes in the adult man of 30 

 cannot affect his structure when he was a boy or child ; nor do I 

 imagine that Dr. Hurst means this, though his sentence seems to 

 imply it. If, however, he wishes to say that the more the adult man 

 comes to be unlike his ancestors the more do the premature stages of 

 his descendants undergo a modification of the same " kind," he has 

 obviously admitted the causal relation between ontogeny and 

 phylogeny which he wishes to deny. 



There is another sentence in the same page which puzzles me en- 

 tirely — "in order that any structure of the adult which varies, and hence 

 ceases to exist as an adult structure at all." The word "structure" 

 seems to be open to objection. I presume Dr. Hurst means "character," 

 but then I do not understand the " hence," unless Dr. Hurst wishes 

 to say "and hence ceases to exist solely as an adult structure." An 

 adult " structure " may vary in the direction of becoming greater or 

 less, and yet may remain an adult " structure," but it will not remain 

 solely an adult "structure." By the law of earlier inheritance illustrated 

 in Mr. Bather's table (p. 279), it gradually becomes an adolescent 

 " structure." Thus, if the adult " structure " be x, and it varies in 

 subsequent generations gradually to become 2x, the adolescent 

 " structure " will by then be x ; and as in subsequent generations 

 adult ix becomes 3.1-, the adolescent x becomes 2x. Hereby we 

 obtain a record ; yet Dr. Hurst says that in order to produce a record 

 " as the adult structure varies in one direction, the late stages of 

 development must vary in another direction." The question is, then, 

 what does Dr. Hurst mean by " late stages of development"? and, 

 also, what meaning ought to be attached to the phrase ? The 

 dictionary explains development as " the series of changes in the 

 growth from first to last of an organised being." Obviously, growth 

 includes not only increase as a whole, which in some organisms is 

 continuous throughout life, but it also includes increase in any part. 

 Thus, the growth of hair on man's chest in middle life is part of his 

 development, and the expansion of the stomach in senility is also part 

 of his development. I contend that the late stages of development 

 are the stages of senility ; and that to give the term any other 

 meaning is a mistake, which, I am aware, is not confined to Dr. Hurst. 



Further, I contend that loss of teeth and loss of hair in man are 

 part of his development — though they are strictly retrogressive phases 

 of development. Then under these circumstances I must ask Dr. 

 Hurst what he regards as acceleration of development, because he 

 probably uses the term in a different sense to that in which I have 

 been accustomed to see it employed. 



Lastly, in regard to development, 1 would remark that, in any 

 discussion, it is most important to clearly distinguish the stages of 

 development in ontogeny and the stages of development in phylogeny; 

 for what Dr. Hurst has written fails to convince me that there is not 

 a close connection between the two. 



S. S. Buckman. 



