130 David Day Whitney 



are more cases of the embryos unable to get out of the egg after 

 they are fully formed. They can be seen writhing and twisting 

 inside the egg and sometimes lived there as long as seven days. 



These cases of abnormalities were due perhaps to the food 

 material in the egg being displaced and therefore unable to nourish 

 certain muscles which are well supphed with food material in the 

 normal embryo. Consequently the young animal was weaker 

 in certain parts of its body. 



In a few cases the eggs began to develop but apparently soon 

 ceased and never produced embryos which showed any cihary 

 movement. In normal embryos the ciliary movement around 

 the head can be seen several hours before hatching. Whether 

 the early death of such eggs is due to abnormal cleavage, mis- 

 placed egg substance, or misplaced chromosomes in division is 

 not clear. 



It is nevertheless apparent from these experiments that a very 

 high percentage of normal young animals develop from eggs 

 that have been centrifuged in the various stages of their early 

 development. 



V THE PROPORTION OF MALE AND FEMALE PRODUCING FEMALES 

 IN THE FIRST, SECOND AND THIRD GENERATIONS AFTER 

 CENTRIFUGING 



If the dislocation of the egg substances has any influence on 

 sex it should become evident by following the history of individual 

 eggs in which the zones of stratification are differently arranged 

 in their relation to the first cleavage plane. 



The following data give the result of experiments carried out 

 to examine the question. 



Expernnent XXXI. March 5, at 2:15 p.m., a female contain- 

 ing a large egg was centrifuged twenty thousand revolutions. 

 At 3:10 p.m., the egg had been laid and was in the first cleavage 

 stage. The pink zone was entirely included in the smaller cell 



(Fig- 3)- 



On March 6, at 11 a.m., a normal young female was swimming 

 about in the dish. Food was then added. She produced eggs 



