6 THE hen's egg. [chap. 



tion with the remarkable body Lecithin. (Compare Hoppe- 

 Seyler, Hdb. Phys. Cheni. 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. 



1 



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 yellow yolk, thus forming the great mass of the 

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

 different material, known as the white 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 



