233 



experiments. — Seven of these eggs were kept to watch the effect 

 of the formation of the medullary folds on the position of the ovate. 

 At 10 A.M. on Mar. 17, the folds were distinctly developed. In three 

 eggs, the ovates could not be found. In one, the ovate was on the 

 side of the embryo. In one, the ovate was exactly opposite the anal 

 dei)ression. In another, the ovate was on the ventral surface. And 

 in another, the ovate was found at the blastopore pole! 



Up to the time when the neural plate begins to develop, the 

 results of the three experiments just described, are so uniform as to 

 indicate that the extraovate remains a fixed point during this period. 

 But after the development of the neural plate has begun, the ovates 

 come to occupy various positions, in many cases far removed from 

 the point 180" opi)Osite the blastopore. During this period it is 

 clear that the ovate is not necessarily a fixed point. 



2. Ovate produced at, or just above, dorsal lip, 

 immediately after appearance of the latter. 



Experiment 4. Six Chorophilus eggs were pricked just above 

 the dorsal lip, immediately after its appearance, at 11.15 A.M. — 

 position of the ovate is shown in Fig. 16^, side view. At 4.30 P.M. 

 the blastopore is circular, and occupies centre of lower surface. The 

 dorsal lip is much nearer the centre of the lower surface than it was 

 at 11.15 A.M., but the ovate in five eggs has preserved its original 

 distance from the dorsal lip — occupying the position shown in 

 Fig. 16*, side view. In the remaining egg, the position of the ovate 

 is indeterminable. Such a result is open to the interpretation that 

 the ovate moves with the moving lip ; that since it lies within the 

 region of activity (cell proliferation), it is carried along in the direction 

 of growth. 



Experiment 5. Two Chorophilus eggs were pricked in the 

 middle of the dorsal lip, at 3 P.M. (Feb. 15) — position of ovate 

 shown in the mirror image of egg. Fig. 16 l At 9.30 P.M. the blasto- 

 pore was small, circular, and excentric, and the ovale was still at 

 the dorsal lip, Fig. 16*^, mirror image. The result again is open to 

 the interpretation that the ovate is carried along with the moving lip. 



Experiment 6. Two Chorophilus eggs were pricked about 

 midway between the dorsal lip and the upper pole, at 3 P.M. (Feb. 15) 

 — position of ovate shown in Fig. 16^ side view. One of the eggs 

 at 9.30 P.M. was in the condition shown in Fig. 16 s, mirror image. 

 In this egg, the ovate which was not of the smallest, and yet not 

 large, was evidently shifted out of its original relative position, but 



