I'l . aiPTion 01 i <tB. 



The envelope^ exhibit. in . , \\ith tin- Mammalian egg, an 



increase in number, t'i!' to the /"hi p-Mucid: 



i, produced in tin- follicle. there i> >ul>..e.|u.nt ly added .still an. 



econdary rn\,-l..pc. ThU is a thick, rood, L'elatmi.iiH layer, 

 whidi is secreted by tin- wall of the oviduct. and wli;ch become^ 

 swollen in water. 



The jM.lar dillerenti.-.iion. taken, M it. were, in th-- \-ry process 

 of developing in the case of the Amphihia. is f>un<; x pressed 



in our tliir.l cxainplr. the /;/// '.v 



In ordor to form a correct picture of the c 

 in the case of the Hen, or of any t.i> 



other hirtl. wo must seek it while 

 still in the ovary, at the moment 

 \\lien it has finished its growth, 

 and is ready to be set free from the 

 follicle. It is then ascertained that 

 only the >pheruidal yolk, the so- 

 called yellow of the egg, which in 

 it.M-lf is an enormously large cell 

 , Big. 6a), is ,l,veloped in the botryoi.U! 



ovary. It is enclosed in a thill but 



tobn% lirm pellicle (,/./,). the 



vitelline membrane, the rupture of 



which is followed by an extrusion of the soft pulpy contents. By 



careful examination one will discover upon the latter a small \\ 



. ihe i:eniiinative disc (k.sch), or discus proliyerus, also calle.; 



catricula. It has a diameter of about 3 or 4 mm., and consists 

 of formative yolk, a finely granular protopla>m with small 3 

 spherules, which alone is involved in the process of cleavage. In 

 he tlattened L r fi minative disc is also found the gerniinative \< 

 iig. '">u (/.-./>) and lig. 6b (x), which is likewise somewhat tlattened and 

 lenticular. 



The remaining chief mass of the eg.u'-i'ell is nutritive yolk, which 

 is c.miposrd <f numherle-s yolk->pherules united by >liu'ht trad 



plasm, as though by a cement, information . 



struct UTV is to bo gained from thin '-ned 



which should he cut perpendicularly to the .irerminative disc. 

 According to differences in staining. ementary composit 



there are now to bo distinguish. ite and the yellow nutritive 



yolk (fig. Ca). 



The white yolk ('.'-!) is present in the egg cell only in a small 



tive disc; i-.6, genuinativ* vewcle; 



