98 EVOLUTION AND NATURAL THEOLOCY. 



It was mentioned in the last chapter that 

 many structures which are very important in 

 some animals, exist as useless rudiments in 

 others. This is still more remarkable in Em- 

 bryology, for teeth which never cut through 

 the gum may be detected in the embryos of 

 whales, and even in those of some birds,* and 

 these absolutely useless organs are subsequently 

 absorbed. 



In the human embryo, the brain resembles 

 that of an embryonic fish. The bloodvessels are 

 also formed on the plan of those of a fish ; and 

 organs which resemble the permanent kidneys 

 of fishes perform a similar office in the human 

 embryo, until they are superseded, before birth, 

 by the true kidneys. f It must, however, be 

 remembered that an embryo should only be 

 compared with other embryos, and that it 

 would be a mistake to suppose that a human 

 embryo, for example, resembles an adult fish 

 or reptile. The approximate fact is that the 

 embryos, after continuing to resemble each 

 other for a time, finally branch off along 



* Darwin, " Origin of Species," pp. 482, 483. 



t Murphy, " Habit and Intelligence," vol. i. pp. 257, 258. 



