EVIDENCES OF EVOLUTION 51 



all, except that the first one becomes the 

 Eustachian tube connecting the ear with the 

 back of the mouth. There is no known inter- 

 pretation of these except as recapitulations of 

 the respiratory apparatus of remote aquatic 

 ancestors. 



Every one is familiar with the bony flat- 

 fishes, such as plaice, flounder and sole, which 

 have an asymmetrical body flattened from 

 side to side. They rest and swim on their 

 right or left side, which is unpigmented, and 

 both eyes are on the upturned pigmented side. 

 Now these markedly asymmetrical fishes begin 

 their life with perfect symmetry just like other 

 fishes. They retain this for some considerable 

 time and live near the surface. At a certain 

 stage a very remarkable lop-sidedness of 

 growth and alteration of equilibrium sets in; 

 they begin to sink towards the bottom, the 

 eye on the down-turned side travels round, 

 or even in part through, the margin of the 

 head; in short, a metamorphosis occurs. 

 Different naturalists may read different mean- 

 ings into the word " recapitulate," but in some 

 sense it is surely true that these flat fishes 

 recapitulate in their early development the 

 form of symmetrical ancestors. 



We have already referred to the case of the 

 baleen whale, which has two sets of teeth in 



