256 RUDIMENTAEY, ATROPHIED. [Chap. XIV. 



mae of male mammals^ which have been known to be- 

 come 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 some- 

 times rudimentary, and sometimes well-developed in the 

 individuals of the same species. In certain plants hav- 

 ing separated sexes Kolreuter found that by crossing 

 a. species, in which the male flowers included a rudiment 

 of a pistil, with an hermaphrodite species, having of 

 course a well-developed pistil, the rudiment in the hy- 

 brid offspring was much increased in size; and this clear- 

 ly shows that the rudimentary and perfect pistils are es- 

 sentially alike in nature. An animal may possess various 

 parts in a perfect state, and yet they may in one sense 

 be rudimentary, for they are useless: thus the tadpole 

 of the common Salamander or Water-newt, as Mr. 6. H. 

 Lewes remarks, " has gills, and passes its existence in 

 " the water; but the Salamandra atra, which Hves high 

 " up among the mountains, brings forth its young full- 

 " formed. This animal never lives in the water. Yet 

 " if we open a gravid female, we find tadpoles inside her 

 "with exquisitely feathered gills; and when placed in 

 "water they swim about like the tadpoles of the 

 "water-newt. Obviously this aquatic organisation has 

 "no reference to the future life of the animal, nor 

 "has it any adaptation to its embryonic condition; it 

 "has solely reference to ancestral adaptations, it 

 "repeats a phase in the development of its progeni- 

 " tors." 



An organ, serving for two purposes, may become 

 rudimentary or utterly aborted for one, even the more 



