322 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



free larvae. They disappear at least a week before the sexual larvae 



are set free from their envelopes. 



The Honeybee (Apis mellifica L.) 



The egg of the hive bee is elongate 

 cylindriform, slightly convex ven- 

 cc trally and concave dorsally, with a 

 finely sculptured reticulate surface. 

 The micropylar area is apparently 

 located at the anterior end, since the 

 cleavage cells first form near the 

 cephalic pole of the egg (Fig. 276). 

 The cells multiply rapidly and mi- 

 grate toward the surface where they 

 form the blastoderm. A few remain 

 behind to form the primary yolk 

 cells. As the cleavage cells approach 

 the surface of the egg, their nuclei 

 assume a peripheral position in the cells. The inner ends of the cleavage 

 cells at first remain united below the cortical layer, thus forming an inner 

 cortical layer (Fig. 277). The inner cortical layer is in part absorbed 



Fig. 27ij.— Apis. Laily cleavage 

 stage. Longitudinal section, (cc) Cleav- 

 age cells, (y) Yolk. 



Fig. 277.— Apis. Cross section, (bid) Blastoderm, (dr) Dorsal strip, (yc) Yolk cell. 



by the blastoderm cells and in part remains to form a pellicle over the 

 yolk. At first the blastoderm is of nearly uniform thickness but soon 

 becomes differentiated into a thicker ventral and a thinner dorsal por- 



