THEORY OF DESCENT 41 



But we can see that if this carried to extreme, unity 

 lost, Plesiosaurus. Here we have seen the same 

 organ is formed (?) (for) different purposes (ten words 

 illegible) : and if, in several orders of vertebrata, we 

 could trace origin (of) spinous processes and mon- 

 strosities &c. we should say, instead of there 

 existing a unity of type, morphology 1 , as we do 

 when we trace the head as being the vertebrse 

 metamorphosed. Be it observed that Naturalists, 

 as they use terms of affinity without attaching real 

 meaning, here also they are obliged to use meta- 

 morphosis, without meaning that any parent of 

 crustacean was really an animal with as many legs 

 as crustacean has jaws. The theory of descent 

 at once explains these wonderful facts. 



Now few of the physiologists who use this 

 language really suppose that the parent of insect 

 with the metamorphosed jaw, was an insect with 

 [more] so many legs, or that the parent of flowering 

 plants, originally had no stamens, or pistils or 

 petals, but some other means of propagation, and 

 so in other cases. Now according to our theory 

 during the infinite number of changes, we might 

 expect that an organ used for a purpose might be 

 used for a different one by his descendant, as must 

 have been the case by our theory with the bat, 

 porpoise, horse, &c., which are descended from one 

 parent. And if it so chanced that traces of the 

 former use and structure of the part should be 

 retained, which is manifestly possible if not pro- 

 bable, then we should have the organs, on which 

 morphology is founded and which instead of being 

 metaphorical becomes plain and (and instead of 

 being) utterly unintelligible becomes simple matter 

 of fact 2 . 



1 That is " we should call it a morphological fact." 



2 In the Origin, Ed. i. p. 438, vi. p. 602, the author, referring to the 

 expressions used by naturalists in regard to morphology and metamorphosis, 

 says " On my view these terms may be used literally." 



