S8 SECTIONAL ADDRESSES 



helpful, wrote in 1921, ' The idea that form changes in ontogeny were 

 preceded by similar changes in adult ancestry is an illusion.' A few 

 years later (1929) he reiterated the same opinion in a yet more forceful 

 way, saying, ' the theory of adult recapitulation is dead and need no longer 

 limit and warp us in the study of Phylogeny.' 



Though palaeontology has long been the stronghold of the theory of 

 recapitulation, there have not been wanting among its devotees those 

 whose faith in the theory has waned and perished. Thus Spath (1924) 

 with a touch of bitterness against the view he has forsaken writes, ' Of 

 course it may be necessary to assume an inverted geological order if our 

 views of the biological order of ammonites are to continue to be governed 

 by discredited " laws " of recapitulation and omission of hypothetical 

 stages.' Some years later (1933) his attitude seems to have become 

 slightly modified, for he then described the law as merely ' inadequate.' 

 In the same work he gives a useful summary of the views of a long array 

 of previous writers who had expressed doubts concerning the ' law of 

 recapitulation.' 



It should be observed here that the bone of contention is not repre- 

 sented by the word ' recapitulation' but by the word ' adult.' Thus, for 

 example, Garstang (1921), in spite of the apparently uncompromising 

 statement quoted above, writes, ' as differentiation increases combinations 

 of layers, tissues, organs, etc. at successive stages resemble more or less 

 distinctly combinations characteristic of successive grades of evolution 

 represented in phyletic classification. To that limited extent ontogeny 

 epitomises phylogeny, in the true sense of the word recapitulation, i.e. 

 sums up.' Other passages in his writings refer to a like parallelism. 

 Again Spath (1933), speaking out of his wide experience in the handling 

 of cephalopods, says of Perrin Smith that ' he constantly overlooked 

 the fact that by heredity an ammonite was an ammonite, and that 

 like other organisms it had to grow and therefore necessarily had to 

 pass through more primitive stages.' It seems to me that this is no 

 more and no less than a useful but incomplete paraphrase of the term 

 recapitulation. 



On the other hand, Raw, discussing the ontogenies of trilobites, after 

 allowing for the presence of embryonic and larval characters in the 

 Protaspis stage, recognises ' phylogenetic characters of ordinal and family 

 value,' whilst ' in the next or Meraspis stage, as the embryonic and larval 

 characters diminish in strength generic and specific characters appear.' 

 In talking of higher divisions than species. Raw is obviously not thinking 

 of a specific resemblance to any definite adult ancestor, but of a general 

 resemblance such as exists between all the species of a genus, all the 

 genera within an order, and so forth. Evidently he also has in mind 

 grades of evolution, and in that respect his position is similar to that of 

 Garstang and presumably also Spath. Garstang, however, visualises the 

 structure not of primeval adults but of primeval young, whilst Raw quite 

 definitely has in mind the general condition in the adults of the primeval 

 stock. 



The idea of recapitulation in the sense of summing up seems to me, as 

 also to Crow (1926) and Lillie (1930), to be inherent in Von Baer's as 



