PARTHENOGENETIC DEVELOPMENT OF STARFISH EGG. 3 1 3 



examination would lead the observer to believe that the number 

 of chromosomes is fully as great as that in the fertilized eggs. 

 This view might be supported by the fact that many of the chro- 

 mosomes show a form similar to that possessed by those of the 

 fertilized eggs. 



Closer examination of the position and arrangement of the 

 chromosomes in these sections reveals the fact that the bodies 

 have been sectioned. The imaginary superposition of one figure 

 upon the other lends credence to such an idea. 



For these reasons I have been unable to determine the num- 

 ber of chromosomes by actual count. The number I believe to 

 be 18, a statement for which I shall give my reasons later. 



(c) Eggs Treated with C0 2 and Subsequently Fertilized. 

 Sections of these eggs agree with figures that I have already 

 published. The eggs were fertilized and underwent segmenta- 

 tion, the C0 2 simply retarding the rate of development. 



Observations on Other Starfish Eggs Treated with C0 2 . 

 I succeeded in obtaining one lot of eggs which developed after 

 treatment with C0 2 , that contain in all cases only 9 chromosomes. 

 I was unable to obtain a ripe male at the time and so can give 

 no facts as to the fertilization of these eggs. 



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II 12 



Fig. 11. First segmentation C0 2 egg. Early anaphase. 



Fig. 12. First segmentation C0 2 egg. Later anaphase. 



