24 Tlie Descent of Man, Part I 



measles. The vesicula prostutica, which has been observed in 

 many male mammals, is now universally acknowledged to Lo 

 the homologue of the female uterus, together with the con- 

 nected 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. 54 Some other rudimentary structures belonging to 

 the reproductive system might have been here adduced. 55 



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

 unmistakeable. 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. 56 It is no scientific explanation to assert that they 

 have all been formed on the same ideal plan. "With respect to 

 development, we can clearly understand, on the principle of 



54 Leuckart, in Todd's 'Cyclop. words) a mere metaphysical prin- 



of Anat.' 1849-52, vol. iv. p. 14-15. ciple, namely, the preservation " in 



in man this organ is only from " its integrity of the mammalian 



three to six lines in length, but, " nature of the animal." In only a 



like so many other rudimentary few cases does he discuss rudiments, 



parts, it is variable in development and then only those parts which are 



as well as in other characters. partially rudimentary, such as the 



53 See, on this subject, Owen, little hoofs of the pig and ox, which 



' Anatomy of Vertebrates,' vol. iii. do not touch the ground ; these he 



pp. 675, 676, 706. shews clearly to be of service to the 



56 Prof. Bianconi, in a recently animal. It is unfortunate that he 

 published work, illustrated by ad- did not consider such cases as the 

 mirable engravings (' La Thebrie minute teeth, which never cut 

 Darwinienne et la creation dite in- through the jaw in the ox, or the 

 de'pendante,' 1874), endeavours to mammae of male quadrupeds, or the 

 show that homological structures, in wings of certain beetles, existing 

 the above and other cases, can be under the soldered wing-covers, or 

 fully explained on mechanical prin- the vestiges of the pistil and stamens 

 ciples, in accordance with their uses. in various flowers, and many other 

 No one has shewn so well, how ad- such cases. Although I greatly 

 mirably such structures are adapted admire Prof. Bianconi's work, yet 

 for their final puroose ; and this the belief now held by most natural- 

 adaptation can, as I believe, be ists seems to me left unshaken, 

 explained through natural selection. that homological structures are in- 

 In considering the w\ng of a bat, he explicable on the principle of m«r« 

 brings forward (p. 2 IS) what appears adaptation. 

 to me (to use Auguste Comte's 



