234 



still in the direction of cell proliferation. In the other egg, at this 

 time the ovate was not discoverable. 



3. Ovate produced directly o }) p o s i t e dorsal lip, im- 

 mediately after appearance of latter. 



In such experiments, the results obtained vary conspicuously. 

 The results are occasionally directly confirmatory of those described 

 under class 1, more often in apparent contradiction. 



Exi)eriment 7. Five frog eggs (eggs collected, species?) were 

 pricked at G P.M. Mar. 11 — position of ovate shown in Fig. IG'*, 

 mirror view. The ventral lip was outlined by 9.30 P.M., the ovate 

 lying just outside it. The condition of three of these eggs, at 9.30 A.M. 

 the next morning, is shown in Fig. 16^", mirror view. The blasto- 

 pore is small, circular, and centrally placed, while the ovate is still 

 at the periphery of the image, apparently occupying its original po- 

 sition. In the other two eggs, the ovates were not discoverable at 

 this time. The result obtained in this experiment, as in the case of 

 the experiments described under class 1, indicates that both dorsal 

 and ventral lips move, the ovate remaining a stationary point. My 

 experience is however that it is only very rarely that the ovate, when 

 produced opposite the dorsal lip as in this case, retains its position. 

 In the great majority of cases, the ovate according to my inter- 

 pretation, moves with the moving lip, as in the experiment next to 

 be described. 



Experiment 8. Eight Chorophilus eggs were pricked at 

 11.15 A.M. — position of ovate shown in Fig. 1G^\ mirror view. 

 The condition of the lower surface in two of these eggs, at 12.15 P.M., 

 is shown in Fig. 16 ^^^ mirror view. The dorsal half of the blastopore 

 lip at this time is marked out as a sharp edge, while the ventral 

 half appears as a pigmented line. The shape of the blastopore is 

 such as to indicate that the ovate offered an obstacle to the formation 

 of the mid-ventral lip — the blastopore has the "concrescing" shape, 

 the ovate being at the ventral lip. In the remaining six eggs, on the 

 other hand, the condition of the lower surface at 12.15 P.M. is that 

 shown in Fig. 16 ^^ mirror view. The dorsal half of the lip is a 

 sharp edge, the ventral half a pigmented line. The blastopore is 

 circular, and the ovate is at some distance from the ventral lip. In 

 these eggs the ovate had apparently offered no obstacle to the "de- 

 lamination" of the ectoderm, and the ventral lip formed in the normal 

 manner. — Later however when the ventral lip had the character of 

 a sharp edge, and the blastopore had narrowed to a small circle (in 

 or near centre of lower surface), in all eight of these eggs, the ovates 



