54 



there extend several finger-like processes composed of the small germ- 

 band type of cells. These finger-like processes work themselves in 

 between the large blastoderm cells, tending to enclose them in meshes. 

 The significance of this process will be seen in later stages. 



The embryo, as it may now be called, has shortened somewhat 

 in length and at the same time has increased in circumference, so that 

 the large blastoderm cells mentioned in the five-day stage as occurring 

 in hollows on the dorsal and ventral sides of the germ band have 

 been crowded out of these positions, those on the dorsal side being 

 forced into the anterior end of the egg, and those on the ventral 

 side now occupying the postero-ventral part of the egg. These cells 

 contain a great deal of yolk and are evidently absorbed as food, since 

 they gradually disappear in later stages. The ventral side of the 

 embryo now lies next to the vitelline membrane, and the dorsal side 

 is separated from the vitelline membrane by only the single layer of 

 the large heavily-staining blastoderm cells, which now extend well 

 towards the anterior end of the embryo, and which at the posterior 

 end are beginning to be enclosed by the finger-like processes from 

 the posterior end of the embryo. 



In an eight-days stage (Fig. 17) the small cells which originally 

 grew out as finger-like processes from the posterior end of the germ 

 band have increased in number to such an extent that they now enclose 

 all the large heavily-staining blastoderm cells mentioned above and 

 the large multinucleate cells in a perfect meshwork, extending as far 

 forward dorsally and laterally as the large cells extend, that is, al- 

 most to the anterior end of the embryo. At the posterior end these 

 large cells are in a group which becomes thinner as it extends for- 

 ward, until near the anterior end it becomes a layer one-celled in 

 thickness. This group ends posteriorly with the large multinucleate 

 cells. The cells forming the network are very small, but are easily de- 

 tected by the presence of the deeply-staining nuclei. At the posterior 

 end of the embryo where the germ band broke up into the finger- 

 like processes consisting of the small cells, the outermost of these 

 processes, which is now a very thin, delicate membrane, extends back- 

 ward over the large multinucleate cells, and enclosing the group of 

 large heavily-staining cells continues forward to meet the thin layer 

 extending backward on the dorsal side of the embryo, thus forming 

 the dorsal closure, and thus including, as a part of the embryo, the 

 large cells which originated in an entirely different part of the blasto- 

 derm from that which formed the original germ band (PI. Ill, Fig. 

 9). The inner layer of peripheral protoplasm lies just beneath this 

 network, thus enclosing it between two membranes. This inner layer 



