166 



INTERNAL FACTORS 



IV. i 



halves, the dorsal and ventral sides (since the dorsal lip always 

 appears in the region of the grey crescent) and the anterior and 

 posterior ends (since the anterior end is always a little above the 



I . 



3 



W 

 V 



I 



->O -80 -TO -60 -50 -40 -30 -2Q -10 



+30 MO +50 +60 +70 +80 



FIG. 80. Frequency polygon of the angle between the first furrow of 

 the Frog's egg and the sagittal plane of the embryo, n = 889, M = 2-12 

 914, cr = 40-39 -646. 



animal pole) are predetermined in the undivided egg. But the 

 manner in which the material of the egg is cut up by the first 

 two meridional divisions makes no difference to the result. In 



