FORMATION OF POLAR SPINDLE IN BUFO. 8 1 



the angle of each V turned in towards the center of the spindle, 

 the four ends of a pair of chromosomes projecting from the 

 spindle give the appearance of a typical tetrad. The maturation 

 divisions of the chromosomes are represented diagrammatically 

 by text-figures 1-5. 



In my previous paper, three sections from one egg (Figs. 25, 

 26, 27) were given in which the fully formed spindle lay some 



i + 



o 



Diagrams of the maturation divisions of the chromosomes in the egg of Bufo lenti- 

 ginosus. 



distance below the surface of the egg and the chromosomes were 

 in the form of closed rings which were split longitudinally. This 

 egg was undoubtedly abnormal and led to the wrong inference 

 that these chromatin rings were identical with those found in the 

 germinal vesicle just previous to its disintegration. If the 

 split V-shaped chromosomes of Fig. 1 1 were to be spread out 

 in the form of a ring and the second maturation division to take 

 place before the halves of the ring separated, then exactly the 

 same effect would be produced as previously illustrated in Figs. 

 25-27. I can only interpret the ring-shaped chromosomes in 

 this abnormal egg-- the one abnormality I have found in many 

 hundreds of eggs sectioned as due to a delay in the separation 

 of the parts after the two divisions of the chromosomes had 

 taken place. 



According to Carnoy and Lebrun (2, 3) who have published 

 a series of memoirs dealing with the development of the germinal 

 vesicle and the formation of the polar bodies in the eggs of vari- 

 ous Batrachia, the chromatin filaments in the egg of Salamander, 

 Alytcs, Triton, Bitfo and Rana arise from repeated resolutions of 

 the nucleoli in the germinal vesicle. As my own work on Bufo 

 began with the fully formed egg taken from the animal just before 

 the beginning of the hibernation period, I have not yet seen this 



