Figure 31. A four millimeter human embryo. This is 

 one of the smallest human embryos that has ever been 

 photographed. Reproduced by permission of the Anatom- 

 ical Laboratory of Chicago University. 



Figure 32. An older human embryo. The eye Is 

 partly formed. The constrictions back of the eye are 

 to become the gill slits. The knobs in the middle of 

 the embryo and near the tail are the fore and hind 

 limbs just beginning to form. Notice that the tail at 

 this stage is longer than the legs. Reproduced by per- 

 mission of the Anatomical Laboratory of Chicago Uni- 

 versity. 



Figure 33. Turtle embryo of about the same size as 

 the human embryo shown in Figure 32. The eye is much 

 larger and the entire embryo is more advanced. These 

 are all untouched photographs so that no one can have 

 any question as to the actual existence of the structures 

 shown 



