232 



and had a diameter about Vs that of the egg, occupying a central 

 position on the lower hemisphere. Four eggs were preserved at this 

 time. In them and the living eggs, the ovates were seen to be 

 opposite the centre of the blastopore, viz. 180" distant. (During the 

 outlining of the blastopore, the region bounding it becomes pigmented, 

 the pigment even "streaming" in some cases over the yolk plug.) 

 In an hour's time (12 M. — room was warm), the blastopore had 

 perceptibly diminished in size, the yolk plug was protruding, and 

 the egg began to revolve through 90". With this revolution of the 

 egg, the blastopore was brought into the position of a terminal of 

 the horizontal axis, the ovate coming distinctly into view at the edge 

 of the egg, 180^ opposite — as is shown in Fig. 16'-, a view of the 

 egg from above. This was the case with all of the eggs. If we 

 assume that during this experiment, that ovate does not shift its 

 position, the conclusion is that both dorsal and ventral lips grow 

 over the yolk. — After the formation of the neural plate began, the 

 ovates were undoubtedly shifted in position. The light colored neural 

 area had appeared in the operated eggs by 1.30 P.M. Mar. 20, al- 

 though there was no trace of the folds themselves. The ovates in 

 these eggs were no longer 180 "^ from the blastopore, having shifted 

 their position in various directions. It is fair to assume that the 

 shifting of the ovates at this time, was caused by the cell activities 

 (proliferation and change of shape) going on in the region of the 

 neural plate. 



Experiment 2. Eleven Chorophilus eggs were pricked in 

 centre of upper hemisphere, at the time when the dorsal lip had 

 just appeared, 11.15 A.M. In natural position of egg, ovate was 

 difficult to make out; it comes into view of the egg is turned. At 

 5.15 P.M., a small circular blastopore occupies lower pole, with ovate 

 opposite its centre. At 5.45 P.M. the eggs begin to rotate through 

 90", bringing the blastopore and ovate (now^ in plain view at edge 

 of the egg) into position of terminals of the horizontal axis. The 

 conclusion to be drawn from the experiment, is the same as for the 

 preceding. 



Experiment 3. A dozen Chorophilus eggs, in advanced stage 

 of segmentation, were pricked in centre of upper hemisi)here, late in 

 the evening March 15. By the next morning the dorsal lip had 

 appeared, and at 12 P.M. that night the eggs had rotated so as to 

 bring the small circular blastopore into position of a terminal of the 

 horizontal axis. The ovates were on the opposite side, 180*^ distant 

 from the blastopore. The conclusion is the same as for the preceding 



