CHAPTER VII 

 THE RISE OF EMBRYOLOGY 



AFTER the comparative anatomy of Cuvier was 

 well under way came the establishment of embryol- 

 ogy in which von Baer (1797-1876) was the central 

 figure. In 1828, by the publication of his detailed 

 observations on the development of the chick and 

 other animals (1834), he established the germ-layer 

 idea and carried the science of the development of 

 animals to a high level. 



Embryology is supplemental to comparative anat- 

 omy and in its present stage of development is to be 

 classified as a morphological subject. It is not pos- 

 sible to appreciate in its full meaning any structural 

 problem of zoology without the assistance of em- 

 bryological study. The adult condition of an or- 

 ganism is the result of a series of changes, it is, in 

 fact, the last step in a long series of modifications 

 that have occurred in the process of building the 

 body from the single-celled condition of the egg to its 

 completed state. These modifications are so pro- 

 found that often the affinities of the animal can- 

 not be recognized in the modified state, and we 



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