THE VERTEBRATES 453 



held in the uterus many more months in order to afford 

 protection and nourishment while it grows larger and stronger. 

 This later stage after the organs are formed is often called 

 a foetus, so as to reserve the word embryo for the early stages 

 when the egg is forming organs. 



In the limited time available in this course we cannot do 

 more than study the mere outlines of mammalian develop- 

 ment as stated in the foregoing. There are many facts in 

 this line which are especially interesting because of the light 

 which they throw on human life, and for these the reader 

 must be referred to special books, and to college courses in 

 embryology of animals. 



