6 



THE HEN S EGG. 



[chap. 



tion with the remarkable body Lecithin. (Compare Hoppe- 

 Seyler, Hdh. Phys. Chem. Anal.) Other fatty bodies, colouring 

 matters, extractives (and, according to Dareste, starch in small 

 quantities), &c. are also present. Miescher (Hoppe-Seyler, 

 Chem. Untersuch. p. 502) states that a considerable quantity of 

 nuclein may be obtained from the yolk, probably from the 

 spherules of the white yolk. 



Fig. 2. 



A. Yellow yolk-sphere filled with fine granules. The outline of 

 the sphere has been rendered too bold. 



B. White yolk-spheres and spherules of various sizes and pre- 

 senting different appearances. (It is very difficult in a 

 woodcut to give a satisfactory representation of these pe- 

 culiar structures.) 



The yellovsr yolk, thus forming the great mass of the 

 entire yolk, is clothed externally by a thin layer of a 

 different material, known as the wMte yolk, which at 

 the edge of the blastoderm passes underneath the disc, 

 and becoming thicker at this spot forms, as it were, a 

 bed on which the blastoderm rests. Immediately under 

 the middle of the blastoderm this bed of white yolk is 

 connected, by a narrow neck, with a central mass of 

 similar material, lying in the middle of the yolk (Fig. 1, 

 w. y.). When boiled, or otherwise hardened, the white 

 yolk does not become so solid as the yellow yolk ; hence 

 the appearances to be seen in sections of the hardened 

 yolk. The upper expanded extremity of this neck of 



