Centrifugal Force upon Beetles^ E^SS^ 



527 



TABLE VI 

 CaUigrapha higsbyana — Series C.B. 2 



^T , r lAee when cen- Length of time 

 Number of ° ^ ° 



trifuged centrifuged 



experiment ° ° 



Interval 

 between end of! 

 experiment and 



fixation 



Orientation 



Remarks 



Series C.B. 2 — Table VI 



The eggs used in these experiments were laid at 7 p.m. on July 

 19. One egg was fixed at the end of fourteen hours; the others 

 were at the same time placed in the centrifugal machine with 

 their posterior ends toward the axis of rotation and subjected to 

 the usual number of revolutions for one hour. 



C.B. 2, a. Fig. 17 shows the "Keimhautblastem," the pole- 

 disc and the distribution of the nuclei in the control egg, aged four- 

 teen hours. The yolk is not included in this figure, as its distribu- 

 tion is similar to that of the freshly laid egg (Fig. 9). The 

 two groups of nuclei, those which form a more or less regular 

 layer near the periphery and will fuse with the " Keimhautblas- 

 tem" in a few hours producing the blastoderm {pbl. n), and the 

 vitellophags (vt) scattered about in the yolk, are quite clearly 

 marked at this stage. When taken from the centrifugal machine 

 a colorless layer of material was observed at the outer end of the 

 egg; this is the gray cap occupying a position similar to that noted 

 under C.B. 4, e. The color of the egg was deep yellow posterior 

 to the gray cap and gradually faded out toward the inner end until 

 near that pole it was almost colorless. A bright-yellow cap, the 

 vesicular layer, occupied the extreme inner end. A sagittal sec- 

 tion of this egg is shown in Fig. 18. At the anterior end is the 

 heaviest substance in the egg, the gray cap. Just posterior to 

 this we find the largest deutoplasmic spheres which gave to the 

 living egg its bright-yellow color. The spaces among these are 



