PARTHENOGENETIC DEVELOPMENT OF STARFISH EGG. 3 I I 



torial plate of the first segmentation spindle in their entirety (Fig. 

 6), the chromosomes are seen to be of a dumb-bell form, some 

 straight, some slightly bent, and lying with their long axis placed 

 transversely to the spindle fibers. Their number, as may be seen 

 from the figure, would lead one to suspect 36 as the somatic 

 number, but owing to the fact that some of the chromosomes 

 are cut, this may not be stated with certainty. 



In an especially fortunate section passing symmetrically 

 through the long axis of the spindle, it is seen that the chromo- 

 somes have been split longitudinally and drawn out as somewhat 

 slender rods. In drawing this figure I have shown only the 

 chromosomes and parts of chromosomes lying within a short 







Fig. 6. Equatorial plate 1st segmentation fertilized egg. Polar view. 

 Fig. 7. First segmentation fertilized egg. Anaphase. 



Fig. 8. First segmentation fertilized egg. Section through chromosomes as they 

 are drawn out in anaphase. 



focal range, inasmuch as it would have complicated the figure so 

 greatly as to make it unintelligible had the chromosomes lying 

 toward the opposite side of the spindle been added. In this sec- 

 tion again, the full number of chromosomes could not be counted 

 with certainty. 



Finally, in a section passing transversely through the spindle 

 of an egg in the same stage of division as that from which Fig. 7 

 was drawn, it is shown conclusively that the somatic number of 

 chromosomes in this lot of fertilized eggs is 36. 



