338 THE STORY OV THE EARTH AND MAN. 



as would the common, and still more ancient, pro- 

 genitor of tlie Old and New World monkeys. The 

 quadrumana and all the higher mammals are probably 

 derived from an ancient marsupial animal; and this, 

 through a long line of diversified forms, either from 

 some reptile-like or some amphibian-like creature, 

 and this again from some fish-lfke animal. In the 

 dim obscurity of the past we can see that the early 

 progenitor of all the vertebrata must have been an 

 aquatic animal, provided with branchiae, with the 

 two sexes united in the same individual, and with 

 the most important organs of the body (such as 

 the brain and heart) imperfectly developed. This 

 animal seems to have been more like the larvas of our 

 existing marine Ascidians than any other form known/' 

 The author of this passage, in condescension to our 

 weakness of faith, takes us no further back than to an 

 Ascidian, or "sea-squirt," the resemblance, however, 

 of which to a vertebrate animal is merely analogical, 

 and, though a very curious case of analogy, altogether 

 temporary and belonging to the young state of the 

 creature, without affecting its adult state or its real 

 affinities with other mollusks. In order, however, 

 to get the Ascidian itself, he must assume all the 

 " conditions '^ already referred to in the previous part 

 of this article, and fill most of the gaps. He has, 

 however, in the " Origin of Species '' and " Descent 

 of Man,'' attempted merely to fill one of the breaks 

 in the evolutionary series, that between distinct 

 species, leaving us to receive all the rest on mere 



