DEVELOPMENT OF THE EGG. 607 



of the embryo of the hen have been made by LiEBERMANN. 1 From 

 his researches we may quote the following: In the earlier stages of the 

 development, tissues very rich in water are formed, but upon the con- 

 tinuation of the development the quantity of water decreases. The 

 absolute quantity of the bodies soluble in water increases with the develop- 

 ment, while their relative quantity, as compared with the other solids, 

 continually decreases. The quantity of the bodies soluble in alcohol 

 quickly increases. A specially important increase is noticed in the fat, 

 whose quantity is not very great even on the fourteenth day, but after 

 that it becomes considerable. The quantity of protein bodies and albu- 

 minoids soluble in water grows continually and regularly in such a way 

 that their absolute quantity increases, while their relative quantity 

 remains nearly unchanged. LIEBERMANN found no gelatin in the embryo 

 of the hen. The embryo does not contain any gelatin-forming substance 

 until the tenth day, and from the fourteenth day on it contains a body 

 which, when boiled with water, gives a substance similar to chondrin. 

 A body similar to mucin occurs in the embryo when about six days old, 

 but then disappears. The quantity of hemoglobin shows a continual 

 increase compared with the weight of the body. LIEBERMANN found 

 that the relation of the hemoglobin to the body weight was 1:728 on 

 the eleventh day and 1 : 421 on the twenty-first day. 



By means of BERTHELOT'S thermometric methods TANGL 2 has deter- 

 mined the chemical energy present at the beginning and end of the 

 development of the embryo of the sparrow's and hen's eggs. The 

 difference was considered as work of development. He found that the 

 chemical energy necessary for the development of each gram of ripe hen's 

 embryo (Plymouth) was equal to 0.805 Cal. This energy originated 

 chiefly from the fat. Of the total chemical energy utilized, about 70 

 per cent was used for the embryo and about 30 per cent remained in the 

 yolk. Of the utilized energy about two-thirds was used in the con- 

 struction of the embryo and about one-third transformed into other 

 forms of energy as work of development. 



By their investigations on the development of the trout egg TANGL 

 and FARKAS 3 have found that the loss in weight of each egg which had 

 an average weight of 88 milligrams was 4.9 milligrams during the 42 

 days of incubation, of which 4.11 milligrams was water and 0.722 milli- 

 gram dry substance with 0.367 milligram C. The eggs lose no nitro- 

 gen and no fat. The fat content increases a little, and indeed, as these 

 authors believe, at the expense of the proteins. The chemical energy 

 used during development was 6.68 gram-calories. 



The highly interesting investigations made by LOEB upon the fer- 



1 1. c. 2 Pfluger's Arch., 93 and 121. 3 Pfliiger's Arch., 104. 



