1 86 THE EMBRYOLOGY OF THE HONEY BEE 



.-Hyp 



Oen 



FIG. 71. Right half of a transverse section through the posterior por- 

 tion of the fourth trunk segment of an embryo. Stage X, showing the 

 location and relative size of the cell-clusters which produce the oenocytes, 

 x 367- 



ing a sharp contraction of the ectoderm at this point. Even at 

 this stage some of the cells of the clusters are seen to be detach- 

 ing themselves and migrating inward. These cells are in all 

 probability the embryonic oenocytes (Oen). At Stage XI the 

 external evidences of an invagination have almost disappeared, 

 only a minute depression marking the point where it had existed. 

 The oenocytes are now seen to be slightly larger than the cells 

 of the ectoderm and are moving inward into the body cavity. This 

 is fairly well shown by figure 726. Certain other sections illus- 

 trate this particular point somewhat more clearly, but the section 

 also shows another important but also unfortunate circumstance, 

 that is, the similarity of the oenocytes at this stage to the adjacent 

 mesoderm cells, particularly those of the fat body (iF, 2p). This 

 similarity is so close that the continuity of the cells seen at Stage 

 X with the oenocytes as they appear in the late embryonic stages 

 (XIII, XIV), as well as of the larval stages could not be demon- 

 strated, in spite of repeated attempts. Graber (1891) encoun- 

 tered the same difficulty in Hydrophilus. Nevertheless, in view 

 of the developmental history of the oenocytes in those forms in 



