SECTION C— GEOLOGY. 



DEVELOPMENT AND EVOLUTION 



^ ADDRESS BY 



PROF. H. H. SWINNERTON, D.Sc, 



PRESIDENT OF THE SECTION. 



Those whose memories carry them back to student days at the end of 

 the nineteenth century will remember how simple and straightforward 

 the relationship between Development and Evolution seemed to be. 

 ' The development of the individual,' we were taught, ' repeated the 

 history of the race,' or more technically and concisely, ' Ontogeny repeats 

 phylogeny.' To us, mere students, the names of Von Baer and Haeckel 

 were in some way mixed up with all this, but we were not very clear 

 what their respective contributions were, except that Von Baer lived long 

 before Haeckel and therefore, we thought, his views must of necessity be 

 a little out of date. But even then there were voices, like that of Hurst 

 (1893), that spoke of a fundamental difference between the views of these 

 two great workers, and maintained that Von Baer was nearer the truth 

 than Haeckel. That diiference is now much more clearly appreciated 

 and finds expression in a tendency towards the division of thinkers into 

 separate camps. On the one hand there are those who may be described 

 as the lineal descendants of Von Baer, who propounded the view that 

 * the young stages in the development of an animal are not like the adult 

 stages of other animals lower down the scale but are like the young stages 

 of those animals.' On the other hand there are the corresponding 

 descendants of Haeckel who maintained that ' the adult stages of the 

 ancestors are repeated during the development of the descendants, but 

 are crowded back into the earlier stages of ontogeny, therefore making 

 the latter an abbreviated repetition of Phylogeny ' (v. de Beer). This is 

 variously referred to as the Theory of Recapitulation, the Principle of 

 Palingenesis and the Biogenetic Law. 



Year by year students of fossils, more especially those concerned with 

 the invertebrates, have discovered an increasing body of facts which seem 

 to them to fit in with and give support to Haeckel's theory of recapitula- 

 tion. Meanwhile students of living forms have, as the result of new as 

 well as old methods of inquiry, accumulated much additional evidence 

 which seems to give the lie to this principle. Thus Garstang, whose 

 survey of this field from the biological point of view has proved most 



