49 



level of the distal ends of the mature cells. This view of the func- 

 tion of the syncitial layer is further supported by the fact that in 

 two places in this layer there are longitudinal thickenings containing 

 many more nuclei extending from the anterior end backward as far 

 as the end of the germ band, and these thickenings occur near the 

 lateral edge of the germ band, or where there is greater need for 

 rapid cell-formation. Furthermore, a larger number of the cells of 

 the germ layers are connected at their bases with the syncitial thick- 

 ening than with any other equal area of the layer. This is shown 

 by Figure lo, which represents a cross-section through the posterior 

 part of the germ band at this stage, that is, just a little in front of 

 the middle of the blastoderm. It will be noticed that there are large 

 blastoderm cells on the dorsal side, showing that here this layer has 

 grown farther forward on the dorsal side than the point on the ven- 

 tral side where the blastoderm cells meet the posterior end of the 

 germ band, which in this stage is about the middle of the egg. Figure 

 II represents a transverse section of the same egg taken farther for- 

 ward, through the region where there is still a small area on the 

 dorsal side that is not as yet covered by the blastoderm cells; the 

 dorsal side of the section is limited, consequently, by the thin pro- 

 toplasmic layer mentioned above. 



In Figures g, lo, and 1 1, most of the cells, both of the germ band 

 and of the blastoderm outside the germ band, are seen to contain 

 a very large number of yolk granules which ha\'e passed through the 

 protoplasmic layer into the bases of the cells. The large cells of the 

 blastoderm especially are distended with the yolk granules, the amount 

 of yolk in many cases being greater than the amount of protoplasm. 

 At this stage many of the yolk granules have broken down, leaving a 

 granular liquid mass. The stellate yolk cells have almost disap- 

 peared, only a few being found scattered throughout the yolk mass. 

 At the posterior end of the section shown in Figure g may be seen a 

 group of cells lying just inside the blastoderm which are smaller than 

 the cells of the blastoderm. Also, in view of their later development, 

 mention should here be made of certain cells in the posterior ventral 

 part of the blastoderm which have become very greatly enlarged, 

 and at their bases contain a large number of yolk granules. The 

 protoplasm in thc^ie cells is denser than in those just at the end. One 

 such cell is shown in Figure 9. 



An examination of the section shown in Figure 11, shows that 

 the cells in the middle of the germ band at this jwint have taken on 

 a different appearance from those at the sides. Instead of the narrow 

 columnar cells with their nuclei out at their extreme distal ends 



