DYNAMICS OF MORPHOGENESIS 441 



lower than, that in corresponding regions of intact animals. 

 During the following thirty-six to forty-eight hours the rate of 

 metabolism remains about the same in the pieces. 



7. After three or four days the rate of metabolism in the pieces 

 begins to rise slowly as reconstitution proceeds. This rise in 

 rate is relatively permanent and constitutes physiological re- 

 juvenescence. It disappears only as the animal increases in size 

 and becomes older with feeding. Its amount depends upon the 

 degree of reconstitutional change and the size and region of the 

 piece. Provided complete reconstitution occurs the degree of 

 rejuvenescence is greater in posterior than in anterior and in small 

 than in large pieces. 



LITERATURE CITED 



Child, C. M. 1911 a A study of senescence and rejuvenescence based on ex- 

 periments with Planaria dorotocephala. Arch. f. Entwickelungsmech., 

 Bd. 31, H. 4. 



1911 b Experimental control of morphogenesis in the reguhition of 

 Planaria. Biol. Bull., vol. 20, no. 6. 



1911 c Studies on the dynamics of morphogenesis and inheritance in 

 experimental reproduction. I. The axial gradient in Planaria doroto- 

 cephala as a limiting factor in regulation. Jour. Exp. Zool., vol. 10, 

 no. 3. 



1911 d Studies, etc. II. Physiological dominance of anterior over 

 posterior regions in the regulation of Planaria dorotocephala. Jour. 

 Exp. Zool., vol. 11, no. 3. 



1911 e Studies, etc. III. The formation of new zooids in Planaria 

 and other forms. Jour. Exp. Zool., vol. 11, no. 3. 



1912 a Studies, etc. IV. Certain dynamic factors in the regulatory 

 morphogenesis of Planaria dorotocephala in relation to the axial gradient 

 Jour. Exp. Zool., vol. 13, no. 1. 



1913 a Studies, etc. V. The relation between resistance to depress- 

 ing agents and rate of metabolism in Planaria dorotocephala and its 

 value as a method of investigation. Jour. Exp. Zool., vol. 14, no. 2. 

 1913 b Certain dynamic factors in experimental reproduction and 

 their significance for the problems of reproduction and develojiment. 

 Arch. f. Entwickelungsmech., Bd. 35, H. 4. 



1913 c Studies, etc. YI. The nature of the axial gradients in Pla- 

 naria and their relation to antero-posterior dominance, polarity and sym- 

 metry. Arch. f. Entwickelungsmech., Bd. 37, H. 1. 

 1913 d The asexual cycle of Planaria velata in relation to senescence 

 and rejuvenescence. Biol. Bull., vol. 25, no. 3. 

 Tashiro, S. 1913 A new method and apparatus for the estimation of exceedingly 

 minute quantities of carbon dioxide. Amer. Jour. Physiol., vol. 32, 

 no. 2. 



