i YOLK 3 



animal, during tin- early stages of its development, from the need of 

 1 ui viug to fend for itself. And, correlated with this, the necessity 

 r developing nimv r 1< 

 complicated adaptive fea- 

 luivs to fit it for survival 

 ii Independent free- 

 living rival ure in these 

 early stages is a, voided. 



The yolk consists occa- 

 sionally of fluid but more 

 usually of rounded or 

 sub - angular granules of 

 highly nutritious material. 

 The yolk granules are 

 frequently of a character- 

 istic colour, yellow or 

 salmon colour or greenish, 

 and these impart their 

 colour to the egg as a whole. FIG : 



Where however the yolk A -section through egg of Am,.i, ;,..,;*. 



becomes very finely Sllbdi- After Cerfontaine, 1 906.) 



vided We filld, as in the Case The small crosses mark the position of apical and abapical 



of Coloured flaSS ground P les - Near the apical pole is seen the second polar body 



, -i v adherent to the surface of the egg. The egg- and sperm- 



intO pOWder, that the Char- nuclei have not yet f use d, and are seen in closejproximityito 



acteristic colour is replaced one another. 



by white. This fine 



subdivision of the s n - 



yolk with its accom- ^r 



panying white colour -^N 



is commonly found 



in parts of the egg 



where metabolism is 



particularly active, 



for example those 



portions in which 



active growth or cell 



division is about to 



take place, the fine - /-Kv'-";'-' y*'"^:''""*i "/>' 



subdivision making " r 'r:^iv*--/."'\'"*V'";. : :l : : 



the yolk readily ^3$:?:g#sg$$:< 



assimilable and so 



available for meta- B. Section through egg ot / r, showing more marked 



hnlin 'Prl WhprP ten.U-n.-y lor the yolk -ranulos t., concentrate towards 

 the abapical pole (Telolecithal condition). 



the yolk is com- 



J ,, n, nucleus. p, pigm.Mit. 



paiatlVely Small in Tne yolk grannies are Indicated In both flgnrea by dark doU. 



amount, as in Am- 



phioxus (Fig. 1, A), it may be distributed nearly equally through- 

 out the egg substance; in other words there is an approach 



