I-] 



SEGMENTATION. 

 Fig. 6. 



19 



l> ^^ 



Surface Views of the early Stages of the Segmentation 

 IN A Fowl's Egg. {A and G after Coste.) 



A represents the earliest stage. The first furrow (5) has 

 begun to make its appearance in the centre of the germinal disc, 

 whose periphery is marked by the line a. In B, the first furrow 

 is completed nearly across the disc, and a second similar furrow 

 at right angles to the first has appeared. The disc thus 

 becomes divided somewhat irregularly into quadrants by four 

 (half) furrows. In a later stage ((7) the meridian furrows h have 

 increased in number, from four, as in B, to nine, and cross 

 furrows have also made their appearance. The disc is thus cut 

 up into small central (c) and larger peripheral (d) segments. 

 Several new cross furrows are seen just beginning, as ex. gr. close 

 to the end of the line of reference d. 



appearance, running, across the germinal disc, though 

 not for the whole breadth, and dividing it into two 

 halves (Fig. G, A). This primary furrow is succeeded 

 by a second at right angles to itself. The surface thus 

 becomes divided into four segments or quadrants (Fig. 

 6,-B). 



2—2 



