Chap. XIV.] EUDBIENTAEY OKGANS. 255 



many descendants from some one ancient progenitor, 

 having appeared at a not very early period" of life, and 

 having been inherited at a corresponding period. Em- 

 bryology rises greatly in interest, when we look at the 

 embryo as a picture, more or less obscured, of the 

 progenitor, either in its adult or larval state, of all the 

 members of the same great class. 



Rudimentary, Atrophied, and Aborted Organs. 



Organs or parts in this strange condition, bearing the 

 plain stamp of inutility, are extremely common, or even 

 general, throughout nature. It would be impossible to 

 name one of the higher animals in which some part or 

 other is not in a rudimentary condition. In the mam- 

 malia, for instance, the males possess rudimentary 

 mammas ; in snakes one lobe of the lungs is rudimen- 

 tary ; in birds the " bastard- wing " may safely be 

 considered as a rudimentary digit, and in some species 

 the whole wing is so far rudimentary that it cannot be 

 used for flight. What can be more curious than the 

 presence of teeth in foetal whales, which when grown 

 up have not a tooth in their heads ; or the teeth, which 

 never cut through the gums, in the upper jaws of 

 unborn calves ? 



Eudimentary organs plainly declare their origin and 

 meaning in various ways. There are beetles belonging 

 to closely allied species, or even to the same identical 

 species, which have either full-sized and perfect wings, 

 or mere rudiments of membrane, which not rarely lie 

 under wing-covers firmly soldered together; and hi 

 these cases it is impossible to doubt, that the rudiments 

 represent wings. Eudimentary organs sometimes retain 

 their potentiality: this occasionally occurs with the 



