Centrifugal Force upon Beetles' Eggs 531 



to develop for twenty-seven hours and then preserved. Ext^er- 

 nally the embryo it carried appeared to be normal in every respect. 



It was in a slightly younger stage than that of C.B. 2, c, shown in 

 Fig. 7. Upon sectioning it was found that the vesicular zone had 

 disappeared entirely, that the yolk had segmented and both this 

 and the vitellophags had regained their normal distribution, but 

 that there still remained a small amount of the heavy gray cap. 

 The embryonic tissue seems to have sustained no ill effects from 

 the centrifugal force. 



C.B. 5, d. A normal larva hatched from the remaining egg of 

 this series in the average period, six days. 



series 



CM. 



Two freshly laid eggs of Calligrapha multipunctata placed with 

 their posterior ends inward were centrifuged for sixteen hours at a 

 rate much slower than that applied to the eggs in most of the other 

 experiments. At the end of this period three perfectly distinct 

 zones could be recognized by their colors. The nearly uniform 

 pale-orange color of the normal egg had given way at the inner end 

 to bright orange; at the opposite pole was a whitish cap, while the 

 comparatively large central zone faded gradually from bright 

 yellow at its outer end to pale yellow where it joined the inner 

 orange stratum. 



CM. I, a. An in toto preparation of one of these eggs which 

 was fixed immediately after being taken from the centrifugal 

 machine shows that the three zones do not diflPer in color only, but 

 are composed of three different substances. Sections of this egg 

 show a stratification similar to that already described for C. bigs- 

 byana (C.B. 4, e). The stage of development, however, is unlike 

 that of any egg so far examined. Fig. 20 shows the nuclei aggre- 

 gated in the inner portion of the egg. The "Keimhautblastem" 

 at the sides of the egg and surrounding the folded vesicular zone 

 contains many nuclei producing a kind ot blastoderm. The 

 vitellophags have accumulated in the inner portion of the 

 central zone. Many of these are either dividing by amitosis or 

 seem to have recently completed such a division. 



