KARYOKINETIC FIGURES OF CENTRIFUGED EGGS. 119 



ously by segregation along their entire course (Hartog, '05). 

 Now my experiments give conditions quite similar to magnetic 

 models in this respect, for the reason that the centers displaced 

 at the mesophase are in the condition of maximum force. 



The fact that the experiments deal only with this stage of the 

 karyokinetic figure limits the results in ways that I fully realize. 

 But this is more than compensated by the advantage of knowing 

 the precise stage of the karyokinetic figure with which the opera- 

 tions deal. The attempts to obtain comparable results at other 

 stages have been unsatisfactory, because any other stage is in 

 motion and the control eggs vary so much that interpretation of 

 results becomes very uncertain. 



LITERATURE. 



Foot, Katherine, and Strobell, E. C. 



'05 Prophases and Metaphase of the First Maturation Spindle of Allolobophora 



foetida. Amer. Journ. Anat., IV., No. 2, 1905. 

 Hartog, Marcus. 



'05 The Dual Force of the Dividing Cell. Part I. The Achromatic Spindle 



Figure Illustrated by Magnetic Chains of Force. Proc. Roy. Soc. London, 



Vol. 76, 1905. 

 Lillie, Frank R. 



'02 Differentiation without Cleavage in the Egg of the Annelid Chjetopterus 



pergamentaceus. Arch. Entw'mech., XIV., 1902. 

 '06 Observations and Experiments Concerning the Elementary Phenomena of 



Embryonic Development in Chaetopterus. Journ. Exp. Zool., III., 1906. 

 '08 On the Specific Gravity of Constituent Parts of tbe Egg of Chsetopterus and 



the Effect of Centrifuging on the Polarity of the Egg. Science, N. S., 



XXVII. , June, 1908. 

 '08 A Contribution Towards an Experimental Analysis of the Karyokinetic 



Figure. Science, N. S., XXVII;, June, 1908. 

 '09 Polarity and Bilaterality of the Annelid Egg. Experiments with Centrifugal 



Force. Biol. Bull., XVI., Jan., 1909. 

 Loeb, Jacques. 



'01 Experiments on Artificial Parthenogenesis in Annelids (Chcetopterus) and 



the Nature of the Process of Fertilization. Amer. Journ. Phys., IV., Jan., 



1901. 

 McClendon, J. F. 



'07 Experiments on the Eggs of Chsetopterus and Asterias in which the Chroma- 

 tin was Removed. Biol. Bull., XII., 1907. 

 Mead, A. D. 



'96, '97 The Rate of Cell-Division and the Function of the Centrosome. Biologi- 

 cal Lectures Delivered at the Marine Biological Laboratory of Woods Hole. 



1896 and 1897. Ginn & Co., Boston. 



