226 



THE RATE OF GROWTH 



[CH. 



illustration, which has been often copied, of 0. Hertwig's work on 

 the effect of temperature on the rate of development of the tadpole*. 



«*• «• 2^" «/• 



/*• //" It,' I-.' IV li" If II' lof 9" a" ^ ef s' 



Fig. 65. Diagram shewing time taken (in days), at various temperatures {° C), 

 to reach certain stages of development in the frog: viz. I, gastrula; II, 

 medullary plate; III, closure of medullary folds; IV, tail- bud; V, tail and 

 gills; VI, tail-fin; VII, operculum beginning; VIII, do. closing; IX, first 

 appearance of hind-legs. From Jenkinson, after 0. Hertwig, 1898. 



* 0. Hertwig, Einfluss der Temperatur auf die Entwicklung von Rana fusca 

 und R. esculenta, Arch. f. mikrosk. Anat. li, p. 319, 1898. Cf. also K. Bialaszewicz, 

 Beitrage z. Kenntniss d. Wachsthumsvorgange bei Amphibienembryonen, Ball. 

 Acad. Sci. de Cracovie, p. 783, 1908; Abstr. in Arch. f. Entwicklungsmech. xxviii, 

 p. 160, 1909: from which Ernst Cohen determined the value of Q^q (Vortrdge iib. 

 physikal. C hemic f. Arzte, 1901; English edit. 1903). 



