8 ON EMBRYOLOGY. 



The reader will scarcely fail to notice that the First Part 

 especially is entirely confined to a simple description of 

 observed facts, no attempt whatever being made to interpret 

 their meanings. We have purposely pursued this course, 

 because any interpretation of the facts of the bird's develop- 

 ment is impossible, or at least illusory, till the history of other 

 animals, vertebrate and invertebrate, has been studied. 

 When all the facts are before him the reader will be in a 

 position to judge of the interpretations offered. 



