450 EUDIMENTAEY OEGANS. Chap. XIII. 



vened at a very early age, or by the variations having 

 been inherited at an earlier period than that at which 

 they first appeared. It should also be borne in mind, 

 that the supposed law of resemblance of ancient forms 

 of life to the embryonic stages of recent forms, may be 

 true, but yet, owing to the geological record not extend- 

 ing far enough back in time, may remain for a long 

 period, or for ever, incapable of demonstration. 



Thus, as it seems to me, the leading facts in embryo- 

 logy, which are second in importance to none in natural 

 history, are explained on the principle of slight modifi- 

 cations not appearing, in the many descendants from 

 some one ancient progenitor, at a very early period in 

 the life of each, though perhaps caused at the earliest, 

 and being inherited at a corresponding not early 

 period. Embryology rises greatly in interest, when 

 we thus look at the embryo as a picture, more or less 

 obscured, of the common parent-form of each great class 

 of animals. 



Rudimentary, atrophied, or aborted organs. — Organs 

 or parts in this strange condition, bearing the stamp of 

 inutility, are extremely common throughout nature. For 

 instance, rudimentary mammae are very general in the 

 males of mammals : I presume that the " bastard-wing " 

 in birds may be safely considered as a digit in a rudi- 

 mentary state : in very many snakes one lobe of the lungs 

 is rudimentary ; in other snakes there are rudiments 

 of the pelvis and hind limbs. Some of the cases of rudi- 

 mentary organs are extremely curious ; for instance, the 

 presence of teeth in foetal whales, which when grown 

 up have not a tooth in their heads ; and the presence of 

 teeth, which never cut through the gums, in the upper 

 jaws of our unborn calves. It has even been stated on 

 good authority that rudiments of teeth can be detected 



