235 



were at the ventral lip. The conclusion to be drawn from this ex- 

 periment is that after the ventral lip begins to grow actively over 

 the yolk, the ovate in some of the eggs is shifted nearer the lip, and 

 in all of them is carried along with the moving lip. Precisely similar 

 results were obtained in a number of experiments. 



Experiment 9. It frequently happened when the ovate, which 

 is produced opposite the dorsal lip, is not very small, that the blasto- 

 ])ore in closing occupied a very excentric position in the mirror 

 picture. This was the case, for instance, with most of the eggs 

 operated upon in the following experiment. Twelve Chorophilus eggs 

 were pricked at 10 P.M. (Mar. 10) — position of ovate shown in 

 Fig. 16 1"*, mirror picture. At 1 A.M. the condition of ten of these 

 eggs is shown in Fig. 16 is,^*^, the first figure giving a direct view 

 of the upper surface, the second a mirror picture of the lower 

 surface. The apparent inference to be drawn from this result is that 

 the dorsal lip migrates over the yolk towards (eventually to) the 

 ovate, which remains stationary at the place where the ventral lip 

 forms. The apparent result is in direct contradiction with the results 

 of experiments 1, 2, 3, 7, and is, I believe, to be explained in the 

 following way. In all ten of these eggs the ovate (occupying the 

 same apparent position as in Fig. IQ^^,^*^) at 11 P.M. is distinctly 

 flattened and gives every indication of being pressed 

 firmly against the lower glass (mirror) — in many of these 

 eggs, there is round the ovate a faint "halo" of whitish yolk material 

 that has oozed out. This flattened condition of the ovate was main- 

 tained during the apparent progress of the dorsal lip over the yolk, 

 and still existed at the end of the experiment, 1.20 A.M. The eggs 

 were then examined in a watch glass under a low objective. On 

 turning the egg so as to bring its side up, the flattened condition 

 of the ovate was conspicuous. In removing the eggs from the mirror, 

 by gently sucking or squirting with pipette, it was evident in the 

 case of several of them that there was a slight adherence between 

 the mirror and the lower surface of the ovate. The character of the 

 ovate strongly suggests that in these eggs a pressure exists from 

 above, which forces the ovate down against the mirror — direction of 

 this supposed pressure is indicated by arrow in Fig. 16 1', side view. 

 Assuming that the conclusion drawn from experiments 1, 2, 3, 7, is 

 the true one, and that both dorsal and ventral lips creep over the 

 yolk towards the lower pole, it follows that if the ovate continues to 

 remain at the ventral lip (a common occurrence, as indicated by ex- 

 periment 8), it runs the risk of becoming pressed down firmly against 



