340 QUESTIONS. 



What is the difference in their stems ? What is the use of the Exo- 

 gens? What is said of the presence of the Endogens and Exogens in 

 the life-record ? What difficulty is there in the study of fossil botany? 

 What error is mentioned as having risen from the scantiness of the 

 evidence ? What is said of the veins in the leaves as furnishing a 

 ground of distinction in the classification of vegetable remains ? 



173. Why is the study of fossil zoology more satisfactory than that 

 of fossil botany ? Give in full what is stated about Protozoans. 



174. What are the classes of Radiates ? Why are they so called ? 

 State what is said of them. 



176. Why are Mollusks so called? What does this division in- 

 clude ? How far are Mollusks zoological in their relations ? Why 

 are they of great value in geological investigations ? Why are the 

 Articulata so named ? What does this division include ? What is 

 said of the relations of the Articulata ? What of the variety of their 

 character? 



177. What are the characteristics of the Vertebrata ? 



178. What is said of the spinal marrow of the Vertebrates ? What 

 are the four grand divisions of this portion of the animal kingdom ? 

 What is said of the intellectual qualities of the Vertebrata ? What 

 of their relations, geological and zoological ? What of their relations 

 to the higher orders of the vegetable world ? 



179. What is said of the mode of division of the earth's history ? 

 What is Dana's division? 



180. Give the division of time into five periods, explaining their 

 names. How definite are the boundaries of the ages ? What is said 

 of foreshadowing ? 



181. What examples of foreshadowing are cited ? What is said of 

 the idea on which the ages are named ? 



CHAPTER XHI. 



181. What is said of the fused state of the earth? 



182. What of the time occupied in cooling the earth sufficiently to 

 form a crust ? What of the length of time before life appeared on the 

 earth ? State in full what is said of the floor of the earth's crust. 

 What were the changes that attended the beginning solidification of 

 the earth's crust ? 



1 83. What agency had denudation in this beginning of the forma- 

 tion of land ? Give Dana's statement in regard to the land formed 

 in the Azoic age. What is said of the extent of the lands that then 

 appeared above the surface of the waters ? 



184. What was the shape of North America in the Azoic age? 

 What does Agassiz say of this island ? How was Europe, in contrast 

 with North America, in this age ? 



