Sept., 1917.] Marchand: Notes on Early Stages of Chrysops. 159 



Each single egg is elongate as usual in Chrysops, and slightly 

 curved. It was seen that the concave side of all the eggs was turned 

 in the same direction, that is, towards the edge of the leaf on which 

 the cluster was found. The concave side of the egg corresponds to 

 the ventral side of the embryo. Assuming the fly sits head-down- 

 wards while laying, that is, looking towards the base of the leaf and 

 away from its edge, each egg is deposited in such a way that on leav- 

 ing the body, the ventral surface of each egg is turned backward from 

 the fly. On the other hand, as each egg is fastened to the leaf by its 

 tail end, one should assume that the head-end is the last to leave the 

 body of the fly. In this way the relative orientation of mother animal 

 and embryo could be determined, but the material was insufficient to 

 fully ascertain this relation. 



Every single egg is seen to be somewhat shrunken on its upper 

 pole, and its outer membrane is here contracted in three ridges meet- 

 ing at the tip at about equal angles of 60°. 



On the earliest stages of the development of the eggs I have no 

 data, as the eggs were not examined before July 9, at noon, when they 

 were almost two days old. Plate XII, figs. 3, 4, and 5, show the eggs 

 at this stage. The embryo is plainly visible, occupying only about 

 five sixths of the whole length of the egg, leaving the upper one sixth 

 empty. The entoderm is plainly differentiated. A large mass of 

 yolk covers the greater part of the dorsal side. Headwards on the 

 sides are dark areas probably corresponding to the eyes which have 

 however not yet appeared. 



On the following day, July 10, at 11 P. M., these eggs were in- 

 spected again. The yolk mass had been considerably reduced, still 

 reaching to the posterior end of the egg, and still taking almost two 

 thirds of the entire length. Head and pharynx have become differ- 

 entiated. The eyes have appeared as two black spots on the dorsal 

 side of the pharynx. The anterior region of the embryo has been 

 pushed forward, and the empty portion of the egg is now less than 

 one tenth of its entire length (Plate XII, fig. 6). When an egg is 

 lesioned at this stage, the yolk flows out immediately as it seems to be 

 quite liquid. 



The body segments are not yet distinctly visible. 



On the following day, July 11, at 5:30 P. M., the larva is seen to 

 fill the whole space afforded inside the egg-shell. At this stage, that 



