No. 611] GENESIS OF ORGAXIZATION OF INSECT EGG 651 



closed b}^ tlie mid-intestine, but in this case a dwarf em- 

 bryo has developed without growing around the nutritive 

 material. 



The effects of centrifugal force upon insect eggs are- 

 different from those produced upon the other tj'pes of 

 eggs that have been employed for such experiments. In 

 the eggs of worms,^^ mollusks,^' etc., apparently the ma- 

 terials that undergo stratification under the influence of 

 centrifugal force have no influence upon the ''ground sub- 

 stance" which is "the seat of polarity and pattern of 

 organization of the cell." In the insect egg, the organ- 

 ized protoplasm is almost entirely limited to the cortical 

 layer and this layer may be shifted away from the 

 periphery by a sufficient force and may become massed at 

 the inner light end when an undeveloped egg is cen- 

 trifuged. 



Since the cytoplasm develops in its new situation and 

 proceeds to build up an embryo as nearly normal as is 

 possible under the conditions imposed upon it, it is evi- 

 dent that the ])otencies of the cytoplasmic areas are pre- 

 detentiiiKMl al the time the egg is laid. 



It w.is liopcd l»y means of these experiments with cen- 

 trifugal force to throw the pole-disc gramiles and the 

 cytoi)hism containing them into some otluT part of the 

 egg. If the germ cells arose fi'oiii lhi> iiiMt<'ri;il in its new 

 position the conclusion would have Ix'cii .-oiin iiiciiig that 

 these substances were necessary \\)V the roi'ination of the 

 reproductive cells. I'lH ortuuatcly. aUhouuli tlie cortical 

 layer at tiic |H.-t('ii.u- ciul ua^ ^liiftcd hv the ci'utrifugal 

 force, it was inipo-sihh' to hicate accuratelx- the germ 

 celN in the euihivo. that .iev.'h.ped l^oiil the eu-v that 



