100 



STUDIES IN EVOLUTION 



Lastly, it must be determined whether spines are really 

 hereditable characters, and therefore can be used in studying 

 the phylogenies of groups. No one has yet been able to 

 show any type or set of characters which cannot be trans- 

 mitted from parent to offspring. Hyatt ^* says : " Every- 



74 



Figure 74. — Diagram and table ; showing correlation of stages and condi- 

 tions of development in the spinose individual, in its ancestry, and in time. 



thing is inherited or inheritable, so far as can be judged by 

 the behavior of characteristics." Furthermore, in a review 

 of animal life, extinct and living, no one can fail to be im- 

 pressed with the fact that especially near the close of the 

 life history of a group, or in a series of highly specialized 

 forms, spinose characters are often considered as of supra- 



