Chap. XIII. RUDIMENTARY ORGANS. 451 



in the beaks of certain embryonic birds. Nothing can 

 be plainer than that wings are formed for flight, yet in 

 how many insects do we see wings so reduced in size as 

 to be utterly incapable of flight, and not rarely lying 

 under wing-cases, firmly soldered together ! 



The meaning of rudimentary organs is often quite 

 unmistakeable : for instance there are beetles of the 

 same genus (and even of the same species) resembling 

 each other most closely in all respects, one of which will 

 have full-sized wings, and another mere rudiments of 

 membrane ; and here it is impossible to doubt, that the 

 rudiments represent wings. Rudimentary organs some- 

 times retain their potentiality, and are merely not deve- 

 loped : this seems to be the case with the mammae of 

 male mammals, for many instances are on record of 

 these organs having become well developed in full-grown 

 males, and having secreted milk. So again there are 

 normally four developed and two rudimentary teats in 

 the udders of the genus Bos, but in our domestic cows 

 the two sometimes become developed and give milk. In 

 individual plants of the same species the petals some- 

 times occur as mere rudiments, and sometimes in a well- 

 developed state. In plants with separated sexes, the 

 male flowers often have a rudiment of a pistil; and 

 Kolreuter found that by crossing such male plants with 

 an hermaphrodite species, the rudiment of the pistil in 

 the hybrid offspring was much increased in size ; and 

 this shows that the rudiment and the perfect pistil are 

 essentially alike in nature. 



An organ serving for two purposes, may become rudi- 

 mentary or utterly aborted for one, even the more 

 important purpose ; and remain perfectly efficient for 

 the other. Thus in plants, the office of the pistil is to 

 allow the pollen-tubes to reach the ovules protected in 

 the ovarium at its base. The pistil consists of a stigma 



