3^2 



BIOLOGY AND ITS MAKERS 



velop they become successively more and more complex, 

 and in their shifting history many rudimentary organs arise 



Fig. 108. — Fossil Remains of a Primitive Bird (Archeopteryx). 

 From the specimen in the Berlin Museum. (After Kayser.) 



and disappear. For illustration, in the young chick, devel- 

 oping within the hen's egg, there appear, after three or four 



