256 KUDIMENTARY, ATROPHIED, [Chap. XIV 



mammse 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 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 rudimentary 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. G. H. Lewes remarks, "has gills, and 

 " passes its 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 

 "find tadpoles inside her with exquisitely feathered 

 " gills ; and when placed in water they swim about 

 " like the tadpoles of the water-newt. Obviously tliis 

 " 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 



