254 THE EMBRYOLOGY OF THE HONEY BEE 



arranged in the form of a fine network. A thickened area at the 

 cephalic end of the egg appears to represent a micropylar area. 

 The vitelline membrane is extremely thin and appears to be 

 structureless. The contents of the egg comprise a large quantity 

 of deutoplasmic material or yolk, and a small quantity of proto- 

 plasm. The yolk is principally in the form of spherical globules, 

 the vitelline spheres, composed of a transparent fluid of an un- 

 known chemical nature, not fat nor oil. Within the yolk spheres 

 are much smaller relatively solid bodies, the vitelline bodies. The 

 protoplasm surrounds the yolk spheres, filling the interstices be- 

 tween them, and also forms a thin cortical layer over the surface 

 of the yolk. Within the protoplasm are numerous minute bodies, 

 possibly identical with the Blochmann's corpuscles of certain other 

 insects. 



The cleavage cells at first form a rounded group near the 

 cephalic pole of the egg. They multiply rapidly and soon form 

 an elongated hollow fusiform figure, its smaller end extending 

 toward the caudal pole. As the cells continue to increase in 

 number the figure also increases in size, until the cells at its larger 

 end, on the ventral side near the cephalic pole, enter the cortical 

 layer and begin to form blastoderm. The majority of the cleavage 

 cells finally reach the cortical layer except a few which remain in 

 the yolk to form the primary yolk cells. 



As the cleavage cells approach the periphery of the egg their 

 nuclei assume a peripheral position in the cells. The latter embed 

 themselves in the cortical layer, the latter, together with the 

 cleavage cells, constituting the blastoderm. The central ends of 

 the cleavage cells, however, remain at first united together below 

 the cortical layer thus forming the inner cortical layer. Later 

 this inner cortical layer is cut off from the remainder of the 

 cleavage cells by a structure having the appearance of a basement 

 membrane. Meanwhile the cells of the newly formed blastoderm 

 multiply by mitotic division, the division planes being at first nor- 

 mal to the surface of the egg, but later become oblique, the cells 

 thus becoming wedge-shaped or pyriform. Finally they assume a 

 prismatic form, the nuclei all coming to lie at the same level; 

 the basement membrane disappears, and the greater part of the 

 inner cortical layer is absorbed by the cells of the blastoderm, 



