3o6 KING. [Vol. XVII. 



Although usually turned towards each other, the ends of the 

 chromosomes are generally distinct (Fig. 8, C and E), but it is 

 not uncommon to find a fusion of two chromosomes at one end 

 only (Fig. 8, B). Very rarely at this stage both ends of a pair 

 of chromosomes are united so that a closed ring is formed 

 (Fig. 8, F). 



The number of chromosomes characteristic of the somatic 

 cell of Bufo lentiginosus is twenty-four. There are twelve 

 pairs of chromosomes in the germi7ial vesicle at this stage. If, 

 as believed by Riickert, the paired arrangement of the chromo- 

 somes is due to a longitudinal splitting of single chromatin 

 threads, which takes place at a very early period, possibly 

 during the transition from the oogonium to the oocyte, then 

 there must have been a reduction to one-half the number of 

 chromosomes normal for the species before the longitudinal 

 splitting occurred. On the other hand, if there has been no 

 longitudinal division and but a pairing off of the separate chro- 

 matin threads, then the normal number of chromosomes is still 

 present at this stage in the maturation, and the reduction to 

 one-half the normal number must come in the second polar 

 division. 



The nucleoli are now beginning to disintegrate ; but the 

 changes which take place in them are not simultaneous. The 

 same section of an egg will show a large number of nucle- 

 oli that stain an intense blue and contain but few vacuoles 

 (PL XXVIII, Fig. ii) ; others with a yellowish tinge that take 

 only a faint blue stain and are completely filled with vacuoles ; 

 and still others that no longer show any affinity for stains and 

 appear as yellowish-green, highly refractive bodies, having 

 apparently a thick outer membrane, yet retaining the original 

 outline of the nucleolus (PI. XXVIII, Fig. 12, A). The very 

 smallest nucleoli still appear homogeneous and take the deep 

 carmine stain characteristic of the chromatin. In addition to 

 these nucleoli, there are now found in each germinal vesicle, 

 usually near the periphery, from two to six bodies which are 

 distinguished from the nucleoli by their enormous size {cf. 

 Figs. 9 and 10 with Fig. 11). The youngest stage of these 

 bodies which I have thus far been able to find is seen in 



