256 PwUDtMEXTAEY, ATEOPHIED, [Chap. XIV 



mammae of male mararnals, which have been known to 

 become well ^developed and to secrete milk. So again 

 in the ndders in the genus Bos, there are normally fonr 

 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 rudimentary, 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 flowers included a 

 rudiment of a pistil, with an hermaphrodite species, 

 having of course a well-developed pistil, the rudiment 

 in the hybrid offspring was much increased in size ; 

 and this clearly shows that the rudiment ary and perfect 

 pistils are essentially 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. Gr. H. Lewes remarks, "has gills, and 

 "passes it- existence in the water; but the Salamandra 

 "atra, which lives 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 

 u . 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 ances- 

 '• tral adaptations, it repeats a phase in the development 

 " of its progenitors." 



An organ, serving for two purposes, may become 

 rudimentary or utterly aborted for one, even the more 



