RUDIMENTS. 23 



which they found a similarly convoluted body, though not at the 

 extremity. 



The reproductive system offers various rudimentary structures; 

 but these differ in one Important respect from the foregoing 

 cases. Here we are not concerned with the vestige of a part which 

 does not belong to the species in an efficient state, but with a 

 part efficient in the one sex, and represented in the other by a 

 mere rudiment. Nevertheless, the occurrence of such rudiments 

 is as difficult to explain, on the belief of the separate creation of 

 each species, as in the foregoing cases. Hereafter I shall have to 

 recur to these rudiments, and shall show that their presence gen- 

 erally depends merely on inheritance, that is, on parts acquired 

 by one sex having been partially transmitted to the other. I will 

 in this place only give some instances of such rudiments. It is 

 well known that in the males of all mammals, including man, rudi- 

 mentary mammae exist. These in several instances have become 

 well developed, and have yielded a copious supply of milk. Their 

 essential identity in the two sexes is likewise shown by their oc- 

 casional sympathetic enlargement in both during an attack of the 

 measles. The vesicula prostatica, which has been observed in 

 many male mammals, is now universally acknowledged to bo 

 the homologue of the female uterus, together with the connected 

 passage. It is impossible to read Leuckart's able description 

 of this organ, and his reasoning, without admitting the justness 

 of his conclusion. This is especially clear in the case of those 

 mammals in which the true female uterus bifurcates, for in the 

 males of these the vesicula likewise bifurcates." Some other rudi- 

 mentary structures belonging to the reproductive system might 

 have been here adduced.-'' 



The bearing of the three great classes of facts now given is 

 unmistakable. But it would be superfluous fully to recapitulate 

 the line of argument given in detail in my 'Origin of Species.' 

 The homological construction of the whole frame in the members 

 of the same class is intelligible, if we admit their descent from 

 a common progenitor, together with their subsequent adaptation 

 to diversified conditions. On any other view, the similarity of 

 pattern between the hand of a man or monkey, the foot of a 

 horse, the flipper of a seal, the wing of a bat, &c., is utterly 

 inexplicable.'" It is no scientific explanation to assert that they 



=« Leuckart, in Todd's 'Cyclop, of Anat.' 1849-52, vol. iv. p. 1415. In 

 man this organ is only from three to six lines in length, but, like so 

 many other rudimentary parts, it is variable in development as well as 

 in other characters. 



^° See, on this subject, Owen, 'Anatomy of Vertebrates,' vol. iii. pp. 

 675, 676, 706. 



" Prof. Bianconi, in a recently published work, illustrated by ad- 

 mirable engravings ("La Theorie Darwinienne et la creation dite inde- 

 pendante," 1874), endeavors to show that homological structures, in 

 the above and other cases, can be fully explained on mechanical prin. 



