Page 

 Feedback Factors Affecting Sexual Differentiation in 



Hydra littoralis ......... 337 



W. F. LooMis 



Apparent Rhythmicity in Sexual Differentiation of 



Hydra littoralis 363 



Helen D. Park 



Aging in Coelenterates ....... 373 



Bernard L. Strehler 



Studies on Chemical Inhibition of Regeneration in 



Hydra 399 



Robert E. Eakin 



A Study of Normal and Abnormal Regeneration of 



Hydra 413 



Dorothy B. Spangenberg 



Growth Factors in the Tissues of Hydra . . . 425 



Allison L. Burnett 



Nucleic Acid and Protein Changes in Budding Hydra 



littoralis 441 



Yu-Ying Fu Li and Howard M. Lenhoff 



Index 449 



