C. E. Beecher — Origin and Significance of Spines. 359 



TABLE OF CONTENTS. 



Page 



Introduction . . __ 1 



Law of Variation . . 3 



Definition of Terms _ 5 



Growth of a Spine 6 



Localized stages of growth _ 10 



Compound Spines _ _ 12 



Application of law of morphogenesis 13 



Ontogeny of a Spinose Individual 14 



Phylogeny of Spinous Forms _ 17 



Categories of Origin _ ]25 



A. External Stimuli 130 



B. Growth Force 131 



C. External Restraint 134 



D. Deficiency of Growth Force ._ 135 



I. In response to stimuli from the environment acting on the most 



exposed parts (Ai) _ 250 



II. As extreme results of progressive differentiation of previous struc- 

 tures (A 2 , B 8 ) - -- -.254 



III. Secondarily, as a means of protection and offense (A 3 , B 4 , C 4 , D 3 ) .- 257 



IV. Secondarily from sexual selection (A 4 , B 4 , C 4 , D 3 ) _. 261 



V. Secondarily from mimetic influences (A 6) B 4 , C 4 . D 3 ) - 263 



VI. Prolonged development under conditions favorable for multiplication 



(Bx) 266 



VIL By repetition (B 2 ) 329 



VIII. Restraint of environment causing suppression of structures (Ci) 331 



IX. Mechanical restraint (C_.) 337 



X. Disuse (C s , D„) .339 



XI. Intrinsic suppression of structures and functions (Dj) 344 



Categories of Interpretation 349 



Spinosity a Limit to Variation 349 



Spinosity the Paracme of Vitality 352 



Conclusion 354 



References 356 



Table of Contents 359 



