ORGANIC EVOLUTION 27 



side world. Hundreds of such embryonic structures 

 are known. These were explained as embryonic 

 adaptations and hence falsifications of the ances- 

 tral records. 



At the end of the last century Weismann injected 

 a new idea into our views concerning the origin of 

 variations. He urged that variations are germinal, 

 i.e., they first appear in the egg and the sperm as 

 changes that later bring about modifications in the 

 individual. The idea has been fruitful and is gener- 

 ally accepted by most biologists today. It means 

 that the offspring of a j^air of animals are not af- 

 fected by the structure or the activities of their par- 

 ents, but tlie gerni material is the unmodified stream 

 from which both the parent and the young have 

 arisen. Hence their resemblance. Now, it has been 

 found that a variation arising in the germ material, 

 no matter what its cause, may affect any stage in 

 the development of the next individuals that arise 

 from it. There is no reason to suppose that such a 

 change produces a new character that always sticks 

 itself, as it were, on to the end of the old series. This 

 idea of germinal variation therefore carried with it 

 the death of the older conception of evolution by 

 sujierposition. 



In more recent times another idea has become cur- 

 rent, mainlv due to the work of Bateson and of 

 de Vries — the idea that variations are discontinu- 

 ous. Such a conception does not fall easily into line 



