490 ORIGIN OF SPECIES 



the principle of variations in the many descendants from 

 some one ancient progenitor, having appeared at a not very 

 early period of life, and having been inherited at a cor- 

 responding period. Embryology rises greatly in interest, 

 when we look at the embryo as a picture, more or less ob- 

 scured, 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 mammalia, for instance, the 

 males possess rudimentary mammae ; in snakes one lobe of the 

 lungs is rudimentary ; 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 fcetal 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? 



Rudimentary organs plainly declare their origin and mean- 

 ing 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 in these cases it is impossible to 

 doubt, that the rudiments represent wings. Rudimentary 

 organs sometimes retain their potentiality: this occasionally 

 occurs with the mammae of male mammals, which have been 

 known to become well developed and to secrete milk. So 

 again in the udders in the genus Bos, there are normally four 

 developed and two rudimentary teats; but the latter in our 

 domestic cows sometimes become well developed and yield 

 milk. In regard to plants the petals are sometimes rudimen- 

 tary, and sometimes well-developed in the individuals of 

 the same species. In certain plants having separated sexes 

 Kolreuter found that by crossing a species, in which the male 



