Chap. VII.] THEORY OF NATURAL SELECTION. 317 



spheroid from one facet to another, hardly deserve 

 consideration. One class of facts, however, namely, 

 the sudden appearance of new and distinct forms of 

 life in our geological formations supports at first sight 

 the belief in abrupt development. But the value of this 

 evidence depends entirely on the perfection of the geo- 

 logical record, in relation to periods remote in the his- 

 tory of the world. If the record is as fragmentary as 

 many geologists strenuously assert, there is nothing 

 strange in new forms appearing as if suddenly developed. 

 Unless we admit transformations as prodigious as 

 those advocated by Mr. Mivart, such as the sudden de- 

 velopment of the wings of birds or bats, or the sudden 

 conversion of a Hipparion into a horse, hardly any light 

 is thrown by the belief in abrupt modifications on the 

 deficiency of connecting links in our geological forma- 

 tions. But against the belief in such abrupt changes, 

 embryology enters a strong protest. It is notorious 

 that the wings of birds and bats, and the legs of horses 

 or other quadrupeds, are undistinguishable at an early 

 embryonic period, and that they become differentiated 

 by insensibly fine steps. Embryological resemblances 

 of all kinds can be accounted for, as we shall hereafter 

 see, by the progenitors of our existing species having 

 varied after early youth, and having transmitted their 

 newly acquired characters to their offspring, at a corres- 

 ponding age. The embryo is thus left almost unaffected, 

 and serves as a record of the past condition of the species. 

 Hence it is that existing species during the early stages 

 of their development so often resemble ancient and ex- 

 tinct forms belonging to the same class. On this view 

 of the meaning of embryological resemblances, and in- 

 deed on any view, it is incredible that an animal should 



