So 



THE EMBRYOLOGY OF THE HONEY BEE 



the external surface is seen, but the cells filling it belong to the 

 mesoderm (compare Fig. 26B), as the small size of their nuclei 

 demonstrates. The mesoderm (Meso) extends also a short dis- 

 tance laterad on both sides of the opening. The anterior mesen- 

 teron rudiment {AMR) is represented in this section by a layer 

 of cells two or three deep lying on each side against the inner 

 surface of the lateral ectoderm, above the mesoderm. The 

 ectoderm has the same thickness and relative extent as in the 

 preceding section. 



Figure 31 represents a third section passing through the ceph- 



Fig. 31. Transverse section through the anterior end of an egg. Stage 

 VII, intersecting the posterior margin of the procephalic lobes (ProL) 

 The middle cord (MC) is shown, on each side of which is the neurogenous 

 ectoderm from which the ventral cord is to be formed. The mesoderm 

 (Meso) the amnion (Am) and two or three cells of the anterior mesen- 

 teron rudiment ( AMR) are also shown, x 243. 



alic end of the embryo, a few sections caudad of the last. The 

 ectoderm here is seen to be diminishing slightly in both extent 

 and thickness. In the ventral mid-line is a strip of cells (MC) 

 whose transverse section has somewhat the outline of an hour 

 glass, and represents the point of juncture of the lateral folds. 

 The significance and fate of this strip will be described in the 

 section devoted to the nervous system. Lining the ectoderm is 

 a single layer of mesoderm, broken at two points. High up, 



