90 THE EMBRYOLOGY OF THE HONEY BEE 



proaches that of an ellipsoid, flattened dorso-ventrally, with its 

 long axis lying in the sagittal plane. In many cases in its form 

 and longitudinal extent it approximates the one illustrated in 

 figure 34A, in some it is smaller, while in two cases the cephalo- 

 dorsal body was tongue or club-shaped, its smaller end extending 

 back in the dorsal mid-line for approximately one-third of the 

 entire length of the egg. Its external surface, in the earlier stages 

 forms a part of the external surface of the egg, in later stages 

 it is partly or entirely covered by amnion cells. Its inner surface, 

 usually strongly convex, is indented by the alveolar spaces repre- 

 senting the yolk spheres, while extending out between the inden- 

 tations are delicate protoplasmic processes continuous with the 

 interstitial protoplasmic mesh work (Fig. 34A and C). The ceph- 

 alo-dorsal body is therefore, like the dorsal strip, closely asso- 

 ciated with the yolk. In structure the cephalo-dorsal body appears 

 to be a syncitium, composed of rather clear and somewhat vacuo- 

 lated cytoplasm, within the inner half of which numerous nuclei 

 are embedded. At its posterior edge it becomes continuous with 

 the dorsal strip, as shown in the figure (Fig. 34A). 



In origin the cephalo-dorsal body appears to be little more 

 than a localised swelling of the dorsal strip. At Stage IV and 

 the stages intervening between Stages IV and V the cephalo- 

 dorsal body, as compared with its condition at Stage V, is located 

 somewhat closer to the cephalic pole, is flatter and contains fewer 

 nuclei, being plainly nothing more than the slightly thickened 

 anterior end of the dorsal strip. At about Stage V it increases 

 rapidly in size and in the number of nuclei contained within it, 

 until it attains its maximum size, as shown in the figure, but its 

 connection with the dorsal strip is never lost and is always readily 

 apparent. Moreover, in many cases smaller but similar swellings 

 of the dorsal strip exist at various points on the dorsal mid-line 

 in the anterior half of the egg. One of these is illustrated in 

 figure 20 A. 



The rapid increase of the cephalo-dorsal body in size and more 

 particularly in the number of nuclei contained within it, is difficult 

 to explain. While it is not impossible that it owes its origin in 

 part to cells derived from the yolk, there is no satisfactory evi- 

 dence that this is the case. The nuclei seen in the yolk during 



