428 SENESCENCE AND REJUVENESCENCE 



Godlewski found that in the earlier stages of regeneration the 

 epithelial cells of amphibia show an increase in cytoplasmic in 

 relation to nuclear volume as compared with the cells of differen- 

 tiated normal epithelium, and that the nucleoplasmic relation 

 gradually approaches the norm as regeneration proceeds. From 

 these facts he concludes that the earlier stages in regeneration cor- 

 respond to the period of oogenesis, and particularly that stage of 

 it in which the egg cytoplasm increases in amount, while the later 

 stages of regeneration correspond to the period of embryonic 

 development in which nuclear substance undergoes relative increase. 

 These conclusions only serve, I think, to show how unsafe the 

 nucleoplasmic relation is as a criterion of physiological condition. 

 It is probable that the first effect of stimulation and increase 

 in metabolic rate in these cells is some degree of hypertrophy 

 (pp. 43-44) with increase in the relative volume of cytoplasm, but 

 this is soon followed by divisions with increase in relative nuclear 

 volume. This is the period of dedifferentiation and rejuvenescence 

 and corresponds not to the growth period of the egg, but to the 

 period of rejuvenescence in embryonic development, while the later 

 stages of regeneration correspond to the period of morphogenesis 

 and senescence in the later stages of development. 



REFERENCES 



BUGLIA, G. 



1908. "Sullo scambio gassoso delle uove di 'Aplysia limacina' nei vari 

 period! dello sviluppo," Arch, difisiol., V. 



CONKLIN, E. G. 



1912. "Cell Size and Nuclear Size," Jour, of Exp. Zool., XII. 

 CROCKER, W. 



1906. "Role of Seed Coats in Delayed Germination," Bot. Gazette, XLII. 



1907. "Germination of Seeds of Water Plants," Bot. Gazette, XLIV. 



1909. "Longevity of Seeds," Bot. Gazette, XL VII. 

 ERDMANN, RHODA. 



1908. " Experimentelle Untersuchung der Massenverhaltnisse von 

 Plasma, Kern und Chromosomen in dem sich entwickelnden 

 Seeigelei," Arch. f. Zellforsch., II. 



GODLEWSKI, E., Jr. 



1908. "Plasma und Kernsubstanz in der normalen und der durch aussere 

 Faktoren veranderten Entwicklung der Echiniden," Arch. f. 

 Entwickelungsmech., XXVI. 



