Centrifugal Force upon Beetles^ ^ig^ 



533 



CM. I, h. Fig. 21 represents a surface view of the right side of 

 an egg Hke that just described which was allowed to develop for 

 nine days. The embryo has continued to develop at the inner 

 (posterior) end. Its orientation is normal except that the entire 

 embryo has shifted its position posteriorly so that the posterior end 

 instead of being coincident with the posterior end of the egg is 

 now part way up on the dorsal surface. A small mass of embry- 

 onic tissue is imbedded in the large mass of yolk. Normally this 

 yolk would be surrounded by the embryo and become, included 

 within the mid-intestine; in this case a dwarf embryo has developed 

 without growing around the nutritive material. 



TABLE VIII 



Calligrapha lunata — Series C.L., a 



! I Interval 



Number of jAge when cen- Length of time between end or 

 experiment I trifuged centrifuged experiment and' 



fixation 



Orientation 



Remarks 



C.L. a, I 

 C.L. a, z 

 C.L. a, 3 



C.L. a. 4 



I hour 



o Posterior end 



55 hours toward axis of 



79 hours j rotation 



j 24 days I 



l^ 18 day larval 



hatched in 6 days 



Series C.L. a — Table VIII 



The effects of centrifugal force upon the eggs of C. lunata are 

 shown by this series of experiments. The results, as may be seen 

 from a comparision of the above table and the following descrip- 

 tions, differ only in minor details from those recorded for eggs of 

 C. bigsbyana similarly treated. 



C.L. a, I. This egg was stratified by the centrifugal force into 

 three layers, a gray cap at the outer heavy end, a middle yolk zone 

 with large deutoplasmic spheres at the outer end gradually 

 decreasing in size toward the inner pole and a light vesicular 

 layer at the extreme inner end. Longitudinal sections resemble 

 those of C. M. I shown in Fig. 20. There are a number of nuclei 

 present scattered about among the yolk-granules near the inner 

 end of the middle zone. Each nucleus is approximately in the 



