THE EMBRYOLOGY OF THE HONEY BEE 239 



epithelium of the mid-intestine has covered the dorsal surface of 

 the yolk they begin to appear in greater number, and at Stage XI 

 are seen applying themselves to that portion of the peripheral layer 

 which is in contact with the ventral margins of the epithelium of 

 the mid-intestine, as shown in figure 75. In this figure yolk cells 

 are also seen lying close to the dorsal surface of the yolk. Such 

 peripheral accumulations of yolk cells are noticeable only in the 

 anterior half of the mid-intestine. At Stage XII (Fig. 81) many 

 of the peripheral yolk cells appear to have traveled ventrad in 

 company with the advancing ventral margins of the epithelium of 

 the mid-intestine and are now situated close beneath the un- 

 covered area of the yolk, where they remain until covered over 

 by the walls of the mid-intestine (Fig. 82). A little later these 

 nuclei are seen to become shrunken and distorted and soon after 

 this they disappear completely leaving no trace behind, having 

 been digested and absorbed by the wall of the mid-intestine. 



In addition to the changes described above relating principally 

 to the yolk cells, other changes take place in the yolk between 

 Stages IV and XIV. These concern the vitelline bodies and the 

 protoplasmic meshwork. As early as Stage IX many of the 

 vitelline bodies are seen to have become much enlarged. Careful 

 scrutiny of sections under a high power shows that the vitelline 

 bodies are undergoing a process of fusion, several joining together 

 to form a larger body and such larger bodies in turn joining 

 with one another to form still larger bodies. These compound 

 bodies when first formed are lobate, the lobes corresponding to 

 the vitelline bodies which have taken part in its formation. Later 

 the lobes disappear and the bodies become spheroidal or ovate in 

 form. This process of fusion goes on continuously up to Stage 

 XIII-XIV when the vitelline bodies are but few in number but of 

 large size, some of them attaining a diameter of eight to nine micra. 

 Soon after this they disappear, presumably being digested, and 

 are absent in examples of Stage XV. 



At Stage IX the protoplasmic meshwork of the yolk also begins 

 to show changes, its meshes here and there being seen to have 

 increased in size, indicating coalescence of the vitelline spheres. 

 This coalescence continues slowly but steadily up to Stage XIV, 

 when the protoplasmic network of the yolk is made up of large 



