SECT. 6] 



OF THE EMBRYO 



871 



water in grams increases with its growth. This is shown by the 

 curves in Fig. 220, taken from a number of investigators (Bia- 

 lascewicz; Hasselbalch; Rubner; Iljin; Murray; Liebermann; Pott 

 & Prey er) , which descend very regularly, following an S-shaped course 

 from the beginning of incubation to the end. It is unfortunate that 



I I I I I \ L 



Days Hatching 



I I I \ \ \ I I I I I I t I 



9 10 1112 13 14 15 16 17 

 Fig. 220. 



9 20 21 22 



we have few data before the 5th day. A solitary determination of 

 Bialascewicz indicates that the average value of 94 per cent., which 

 we have at that time, may be a peak rather than a steady level 

 and Schmalhausen, who gives a value of 70 per cent, for the second 

 day, 85 per cent, for the third and 93 per cent, for the fourth, em- 

 phasizes this point. Further investigation is much needed here, but 

 for the greater part of the incubation period the facts are very definite. 

 The obvious corollary of this increasing dryness is that for every 

 N E II 56 



