Ill] 



THE EFFECT OF TEMPERATURE 



115 



10° was (on the average) somewhere about 55-6/16-7, or 3-33, 

 times as long as was required at 20°. 



2#-° ZJ" ii" H' iO" 19' 18° It' 16' l{>' IV 13'' n" II' 10° 9° a" '^ 6° 



Fig. 28. 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.) 



We may then put our equation again in the simple form, 

 xi" - 333. 



8—2 



