The Consequences of Evolution - 571 



Fig. 29-18. Skull and facial restorations of various prehistoric men, by J. H. McGregor. From left to right: 

 1, the Java man, Pithecanthropus; 2, the Neanderthal man; and 3, the Cro-Magnon man. In 1, the lighter 

 parts are restorations, deduced from the anatomy of the other parts. (Courtesy of the American Museum of 

 Natural History, New York.) 



b. stages in the development of the skele- 

 tal system 



c. origin and development of the circula- 

 tory organs? 



9. To what extent does a human embryo in the 

 "gill slit stage" tend to resemble a fully de- 

 veloped fish? 



10. Explain and discuss the theory of recapitula- 

 tion, pointing out its strengths and weak- 

 nesses. 



11. Explain the genetic basis of the recapitula- 

 tion tendency. 



12. Explain how a study of the comparative 



biochemistry of the tissues (for example, 

 blood) of various groups of animals and 

 plants can be used to reveal genetic relation- 

 ships among the groups. 



13. Carefully define: (a) paleontology; (b) a fos- 

 sil; (c) sedimentary rock: (d) erosion; (e) 

 metamorphosis (of rock); (f) a geological 

 stratum. 



14. Explain how it is possible to estimate: (a) 

 the relative age of a given geological stratum; 

 (b) the absolute age of certain strata. 



15. Distinguish between the eras and periods of 

 geological time. 



