Effect of a Centrifugal Force upon Development and Sex 129 



the eggs had hatched. Of the seven remaining eggs one was a 

 winter egg, three were dead parthenogenetic eggs and the other 

 three contained Hving embryos which were apparently unable to 

 break through the egg envelope. 



Lot B. March 14, at 8:40 p.m., twenty eggs were isolated and 

 allowed to remain undisturbed. At 9:10 p.m., these eggs were 

 centrifuged in the same way and treated as Lot A. March 15, 

 at 1 130 p. m., seventeen young normal females were in the dish 

 and three unhatched eggs which contained living embryos. At 

 9 p.m., two of these eggs had produced normal females but the 

 other was still unhatched. 



Lot C. March 14, at 8:45 p.m., thirty eggs were isolated and 

 allowed to remain undisturbed. At 9:45 p.m., these eggs, in 

 some of which the first cleavage and in others the second and 

 third cleavage had appeared, were centrifuged and treated as 

 Lot A. 



March 15, at 1:40 p.m., fourteen normal young females were 

 removed from the dish and sixteen unhatched eggs remained 

 At 9 p.m., seven other normal young females were removed. 



March 16, at 10 a.m , two other normal young females were 

 removed. Seven eggs remained. One was a winter egg, two were 

 dead parthenogenetic eggs and four contained living embryos. 



Lot D (Control). March 14, at 10:30 p.m., thirty-three eggs 

 were isolated. 



March 15, at 12:30 p.m., thirteen normal young females and 

 two normal young males were removed from the dish. At 9 p.m., 

 seventeen other normal young females and one normal young 

 male were remov d. 



In Experiment I the eggs were centrifuged when they contained 

 the germinal vesicle or else the maturation spindle. In Experi- 

 ment XI, Lot A, they were centrifuged in the stage when the polar 

 body is forming or just after it was formed. In Lot B the eggs 

 we e centrifuged just before the first cleavage and in Lot C dur- 

 ing and after the first cleavage. 



In some of these experiments the young animals which de- 

 veloped from the centrifuged eggs seem to die sooner if not fed 

 than do the animals developing from normal eggs. Also there 



