THE GERM-SHIELD. 



297 



rounded off, the other is smaller and more pointed ; the 

 former represents the hinder portion of the future body. 

 The characteristic bilateral form of the body, the distinc- 

 tion between anterior and posterior, between right and 

 left, is thus already indicated. 



In the centre of the light germ-area a dull-coloured, 

 large, oval spot now appears ; at first it is very delicate and 

 hardly noticeable, it soon however becomes more sharply 

 distinguished, and presently appears as an oval shield, 

 surrounded by two rings (Fig. 84). The inner, lighter ring 



Fig. 84. — Germ. area or 

 germ-disc of a Rabbit (aboat 

 ten times magnified). As 

 the delicate, half-transparent 

 germ-disc lies on black 

 ground, the light germ-area 

 appears as a darker ring, the 

 dark germ-area (situated on 

 the outside), on the contrary, 

 as a white ring. The oval 

 germ. shield, situated in the 

 centre, also appears whitish ; 

 along its axis the dark spinal 

 furrow is already visible. 

 (After Bischofe.) 



is the remnant of the 

 light germ-area ; the 

 outer, darker ring is 

 the dark germ-area; but the dull-coloured shield-shaped 

 spot itself is the first rudiment of the dorsal portion 

 of the embryo. We will call it briefly the "germ-shield" 

 (notaspis).^^ Eemak called it the " double shield," because 

 it arises from a shield-shaped thickening of the outer and the 

 middle germ-layers. In most books this germ-shield is 



