46 GEORGINA B. SPOONEE 



Morgan, T. H. 1908 The effect of centrifuging the eggs of the mollusc Cumingia. 

 Science, vol. 27. 



1902 The relation between normal and abnormal devel pment 

 of the embryo of the frog as deformed by injury to the yolk ortion 

 of the egg. Arch. Entwickelungsmech., Bd. 15. 



1906 Influence of a strong centrifugal force on the frog's egg. Arch. 

 Entwickelungsmech., Bd. 22. 



1909 The effects of centrifuging eggs before and during develop- 

 ment. Anat. Rec, vol. 3. 



Whitney, D. D. 1909 The effect of a centrifugal force upon the development 

 of the sex of parthenogenetic eggs of Hydatina senta. Jour. Exp. 

 Zool., vol. 6. 



EXPLANATION OF FIGURES 



1 Cyclops fimbriatus — centrifuged egg, showing the spindle with one pole 

 imbedded in the yolk hemisphere. 



2 Cyclops fimbriatus — egg centrifuged longer than egg shown in fig. 1. Spindle 

 parallel to the layers. 



3 Cyclops fimbriatus — section of egg sac showing distorted spindle in b and c 

 and the astral discs. 



4 Cyclops fimbriatus — egg centrifuged in the anaphase of the two-cell stage, 

 showing a longitudinal section of the spindle in one cell and a cross-section of 

 one of the asters of the spindle in the other cell. 



5 Cyclops fimbriatus — egg centrifuged just before the second cleavage. The 

 laj^ers and spindles are oblique to the first cleavage. 



