DISCUSSION 193 



only to look for phylogenetic reproduction in 

 accordance with heredity. 



He pointed out that Haeckel had used two 

 distinct names to designate these two aspects of the 

 biogenetic principle, viz. Palingenesis, or original 

 reproduction, and Ccenogenesis, or subsequent 

 modification. He admitted that Haeckel's theory 

 had been subjected to much criticism, and that his 

 law had been found not to correspond with ascer- 

 tained facts, inasmuch as the changes undergone 

 by embryos and by young animals were too great 

 to be accounted for thus, and could not be regarded 

 as a reproduction of the evolution of the race. 

 Nevertheless, Father Wasmann himself had recog- 

 nised the importance of the law in several respects, 

 and had adduced the best instances of its applica- 

 bility. 



The speaker made a mistake here. I never 

 recognised the biogenetic principle as such, either 

 in my third lecture or in my book on Biology 

 and the Theory of Evolution. The instances 

 adduced by me, to which Dr. Schmidt-Jena 

 referred, were exceptional cases of relatively 

 rare occurrence, in which the development of the 

 individual gives us a clue to the evolution of 

 the species (see p. 62). But the fact that 

 these cases are exceptional and of rare occur- 

 rence shows that the biogenetic principle is not 

 a general law. The reader is invited to compare 



N 



