OVARY AND OVARIAN OVA IN CERTAIN MARINE FISHES. 147 



converted into any of the structures of the directive spindle, 

 but he suggests it as probable that they form reserves of 

 chromatic substance, which they afterwards give up to the 

 chromosomes. His own description is not very consistent 

 with this suggestion, since he states that the nucleoli increase 

 and decrease synchronously with the increase and decrease in 

 size of the chromosomes. But although, according to various 

 descriptions, the chromosomes of the directive spindle are 

 very much shorter than the chromosomes of the earlier stages 

 of the germinal vesicles, they are much thicker, and much 

 more deeply stained. They contain, therefore, in all proba- 

 bility, more chromatin, and possibly they take up chromatin 

 from the nucleoli when the latter disappear. Possibly the sub- 

 stance of the nucleoli is absorbed into the fibrils. The condi- 

 tion shown in fig. 29 may be a stage in such a process. The 

 stained bodies in this condition have a resemblance to chro- 

 mosomes, but as observers are agreed that the nucleoli are 

 not converted into chromosomes, but that these are identical 

 with the nuclear fibrils, and since the fibrils are present 

 within the ring of stained bodies, it may be inferred that 

 the substance of the latter is about to be transferred to 

 the fibrils. This suggestion can only be tested by further 

 investigations. 



In figs. 7, 8, 9 are shown some stages of the germinal vesicle 

 in the ova of the grey gurnard (Trigla gurnardus). Fig. 7 

 is a section of an ovum -28 mm, in diameter. The prepara- 

 tion from which it is taken was made from material obtained 

 in the fish market on April 26th, and fixed with picro-sulphuric 

 acid. The largest yolked ova are for the most part burst, in 

 consequence of the action of the fixing reagent on the yolk 

 and the vitelline membrane, but the younger ova are well 

 preserved. In those of the stage figured there are numerous 

 small nucleoli on the inner side of the membrane, and verv 

 distinct feathery separate fibrils in the central region of the 

 vesicle. These are of various shapes, sometimes V-shaped, 

 sometimes even circular. The ground substance appears very 

 finely granular. The feathery fibrils are even more distinct 



