﻿Contr. toward the Embryol. and Anat. of Pol. pallipes (Hymenop.). 141 



In Polistes the cleavage nuclei reach the surface first at the 

 anterior end, but just which part is not clear to us. They appear 

 to arrive first near the equator, the blastoderm eells being first 

 formed at the poles, especially at the anterior. Grassi (19) and 

 Dickel (14) both observed that in Apis the blastoderm first forms 

 at the anterior pole and from here extends to the posterior. In 

 Fig. 7 we show a sagittal section of an egg shortly after the cleavage 

 nuclei have reached the surface. The nuclei along the ventral and 

 dorsal surfaces have entered the Keimhautblastem. At the two poles 

 a slightly advanced stage is seen and this extends over the egg for 

 a short distance, further on the ventral than on the dorsal surface. 

 Near the posterior end, and also ventrally, a few nuclei are seen 

 which have only begun to enter the Keimhautblastem. Carriere 

 and Bürger (11) have shown that in Ghalicodoma the same thing 

 occurs, the entrance of the nuclei into the Keimhautblastem not being 

 the same over the entire surface of the egg. 



The blastoderm cells are formed by cell boundaries appearing 

 which cut off the nuclei from each other, resulting in a continuous 

 layer of cells over the egg. The basal boundary is the last formed, 

 the cells being separated from each other before they are cut off 

 from the yolk. In general, it can be said that the nuclei at the 

 poles are separated before those on the rest of the surface. We 

 have observed in eggs not yet showing a distinct layer of blastoderm 

 cells, certain peculiarities in the Keimhautblastem between the nuclei. 

 These are found equidistant between the nuclei; occupying a position 

 corresponding to that at which a little later cell boundaries will 

 occur. In this space between two nuclei rows of small vacuoles 

 could be seeu, these occupying a position corresponding to that at 

 which the boundary will later appear and place the two nuclei in 

 adjacent cells. These rows of vacuoles were always at right angles 

 to the egg's surface (Fig. 34). Sometimes there were a number of 

 small vacuoles; these might in other places be represented by one 

 or two large ones; or both large and small would be fouud in the 

 same row. Again is was noticed that there would be one or two 

 elongated vacuoles, and through the center of each, a gatheriug of 

 slightly darker granules than found in the surrounding Keimhaut- 

 blastem. These central granules were connected with the edge of 

 the vacuole by finer rows of granules (Fig. 35). Both the elongated 

 vacuoles and the rows of granules extended entirely, or in part, 

 between the yolk and the surface of the egg. Again we noticed 



