CORRESPONDENCE. 



Phylogeny v. Ontogeny. 



A CHANCE has enabled me to see Dr. Hurst's reply to my article on "The 

 Recapitulation Theory in Palaeontology." Without reference to his original paper 

 it is impossible for me adequately to examine his argument ; but, that I may not be 

 thought to ignore his defence, I venture to send these lines. 



I am not so sure that I have misunderstood Dr. Hurst's position, despite his 

 assertion that none of my missiles hit it. At any rate, it is clear enough now : he 

 does not deny that, in many cases, individual development may follow the same lines as 

 the evolution of the race ; he merely denies that the past history of its race has any 

 influence on the growth-stages of an individual. Considering the impossibility of 

 producing experimental evidence, such a position is, in strict logic, impregnable. 

 For, let us suppose that the ontogeny of every individual was an epitome of its 

 phylogeny, it would still be open to anyone to deny any causal relation between the 

 two. But, if I remember rightly, Mr. Hurst, in his original paper, maintained that 

 the development of any individual was a regular progress from the embryo to the 

 adult ; modifications of early stages, adaptations to larval environment, might of 

 course occur, but, on the whole, each growth-stage represented an approximation to 

 the adult. Consequently, when race-history consisted in a regular advance from 

 the primitive ancestor to the specialised descendant, then the individual developmei.t 

 must normally repeat it ; ontogeny and phylogeny would necessarily move in the 

 same direction along parallel lines, but there would be no need to suppose any 

 causal relation. But if the history of a race were no such regular advance; if, on 

 the contrary, it could be clearly shown by the evidence of fossils that the race had 

 ascended to an acme and then descended ; if a structure could be seen to appearand 

 disappear during this history ; then it is equally clear that, on Mr. Hurst's 

 hypothesis, ontogeny would not correspond with phylogeny ; it is clear that 

 vanished structures or forms would not temporarily make their appearance during 

 the growth of an individual, unless indeed they were produced by some other cause, 

 as adaptations to a temporary environment. This appeared to me to be Mr. 

 Hurst's position, and the following was the nature of my attack. I adduced 

 instances of structures or forms appearing in the earlier stages of individual develop- 

 ment, and then disappearing ; these characters were not such as could be supposed 

 due to larval adaptation or to any modifying causes of a temporary nature; but these 

 characters could be shown by pal^ontological evidence to have arisen and disap- 

 peared in just the same way in the history of the race. Now, I will merely ask Mr. 

 Hurst to tell me what cause can have produced these deviations of ontogeny from 

 the path of simple development. Unless some plausible explanation can be found, 

 it seems reasonable to suppose that they are due to heredity, and are, in fact, as 

 well as seeming, recapitulations of ancestral history. In Mr. Hurst's reply I see no 

 attempt to meet these difficulties. He merely denies that difficulties exist, and 

 asserts that my shots have all passed by him. Despite his explanations it seems to 

 me that the only reason he has not felt my attack is, because he is encased in. some 

 bullet-proof cloth or other, which has a little dulled his perceptions. 



It is needless to reply to Mr. Hurst's other remarks while the above question 

 remains unanswered. Only with regard to the figures illustrating the ontogeny and 

 phylogeny of Antedon which he suggests should accompany a fuller account in a 



