THE DESCENT OF MAN 61 



They occur to the number of four and three 

 respectively in all mammals and in human beings. 



In the case of fishes they develop eventually into 

 real branchial arches and real branchial clefts. 

 If we consider what becomes of them in the case of 

 the higher vertebrates and man, we find that the 

 first branchial arch becomes the mouth, and the 

 first branchial cleft the exterior ear; the others 

 either undergo involution, or they form various other 

 organs, the bones of the inner ear, etc. 



If we consider the matter in a calm and dis- 

 passionate way, we arrive at the conclusion that, in 

 the case of the higher vertebrates and man, these 

 so-called branchial arches and clefts are merely 

 curves and folds of the pharynx, which are quite 

 unimportant in themselves, and eventually develop 

 into something bearing no resemblance to real 

 branchial arches and clefts. They are, in fact, 

 simply pharyngeal arches and clefts. But in the case 

 of fishes, to whose existence gills are essential, a 

 similar arrangement develops into real gills, and 

 so, with regard to them alone, it is correct to speak 

 of real branchial arches and clefts as existing in 

 the embryo. I can by no means see that these 

 facts constitute an argument in favour of a 

 theory that all mammals, and man in particular, 

 have passed through a fish-like stage of being, nor 

 is there any logical support for such a theory. 



It would be a mistake, however, to assume that 

 I simply reject the biogenetic principle. If it only 



