GROWTH, METAMORPHOSIS AND DEVELOPMENT 265 



since the fertilized and the nonfertilized frog's egg shows, according 

 to L. BACKMANN and J. RUNNSTROM,* only 1/10 of the osmotic 

 pressure of the egg in the ovary, or of the adult frog. In the course 

 of development, the osmotic pressure increases so that in the tadpole 

 of 25 or 30 days, the osmotic pressure is almost the same as in the 

 metamorphosed animal. L. BACKMANN and J. RUNNSTROM agree 

 that the decrease in osmotic pressure is due to the fertilization, which 

 results in a gel formation by means of which crystalloids are adsorb &d. 

 After a certain time, which varies for different animals, but not 

 as yet definitely established for individual ones, a shrinking begins 

 again, as may be seen from the following data, taken in part from the 

 tables of H. GERHARTZ* 1 : 



MAN. 



Water, per cent. 



Dry substances, 

 per cent. 



3d fetal month 94.0 



6th fetal month (Rubner) 90.0 



7th fetal month (Rubner) 86.0 



8th fetal month (Rubner) 83.3 



Newborn (Camerer, Jr.) 71.7 



Adult (Moleschott) 67.6 



Adult (Bouchard) 66.0 



DOG. 



6 days old (Gerhartz) 80.3 



15 days old (Gerhartz) 77.0 



SHEEP. 



6 months old (Lawes and Gilbert) 47.8 



15 months old 43 . 4 



MOUSE. 



Fetus ( inch long) (A. v. Bezold) 87.2 



Newborn (A. v. Bezold) 82.8 



8 days old (A. v. Bezold) 76.8 



Full grown (A. v. Bezold) 73. a 



CHICKEN EMBRYO (without yolk). 



7th day (L. v. Liebermann) 92.8 



14th day (L. v. Liebermann) 87 . 3 



21st day (L. v. Liebermann) 80.35 



6.0 

 9.7 

 14.0 

 16.7 

 28.3 

 32.4 

 34.0 



19.7 

 23.0 



52.2 

 56.6 



12.8 

 17.2 

 23.2 



28.7 



7.2 



12.7 

 19.65 



What constituents are especially deprived of water cannot be 

 properly determined from the limited material at hand, yet, accord- 



