THE DESCENT OR ORIGIN OF MAN 43 



the spinal cord, but tlie lower part apparently consists merely 

 of the pia mater, or vascular investing membrane. Even in 

 this case the os coccyx may be said to possess a vestige of 

 so important a structure as the spinal cord, though no longer 

 inclosed within a bony canal. The following fact, for which 

 I am also indebted to Prof. Turner, shows how closely the 

 OS coccyx corresponds with the true tail in the lower ani- 

 mals: Luschka has recently discovered at the extremity of 

 the coccygeal bones a very peculiar convoluted body, which 

 is continuous with the middle sacral artery; and this discov- 

 ery led Krause and Meyer to examine the tail of a monkey 

 (Macacus) and of a cat, in both of which they found a simi- 

 larly convoluted body, though not at the extremity. 



The reproductive system offers various rudimentary 

 structures ; but these diif er 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. Never- 

 theless, the occurrence of such rudiments is as difficult to 

 explain, on the belief of the separate creation of each spe- 

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

 recur to these rudiments, and shall show that their presence 

 generally 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 mam- 

 mals, including man, rudimentary 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 occasional sym- 

 pathetic 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 be the 

 homologue of the female uterus, together with the connected 

 passage. It is impossible to read Leuckart's able descrip- 

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



