of the Fishery Board for Scotland. 



107 



alteration by the action of the re-agents. In these cases the rays may 

 often be traced passing into the protoplasmic network lying between 

 the yolk-spherules. This is well shown in some sections of the ovary of 

 the plaice, fixed with 5 per cent, solution of nitric acid (Fig. 5, PI. I.). 

 The nuclear membrane in such cases is frequently indistinct. In 

 preparations hardened with picro-sulphuric acid this appearance is less 

 obvious, owing partly to the shrinking of the nuclear substance. At 

 this stage the nucleoli are not, as a rule, so prominent and highly stained 

 as at an earlier period, and they are usually smaller and less numerous, 

 and for the most part disposed around the margin, although many of 

 them lie towards the centre of the germinal vesicle. In the largest 

 opaque eggs in the ovary of a sole, in which fully mature eggs were also 

 present, the nucleoli numbered from five to twelve in a section, and they 

 were of different sizes. In a germinal vesicle, measuring O'lSmm., the 

 ovum measuring O'Glmm., the largest nucleolus measured O'OOGmm. In 

 the ovary of a bib (Gadus luscus), preserved like that of the sole in picro- 

 sulphuric acid and containing mature eggs, the nucleoli were much more 

 numerous, numbering frequently over fifty in a section, but they were 

 also smaller. The disposition and appearance of the nucleoli in the egg 

 of the solenette at this stage is shown in Fig. 7, PI. I. 



I was unable to make out satisfactorily the presence of a chromatin 

 network or threads in the germinal vesicle of these advanced pelagic eggs, 

 although it is distinct in the smaller ones lying beside them. With the 

 exception of the very early stages the nucl^eoli are not of the nature of 

 karyosomes ; they lie as distinct more or less spherical bodies in the 

 nuclear substance. Very frequently they exhibit internal differentiation, 

 showing granulation or vacuolation. In the opaque demersal eggs of the 

 John Dory and angler I was able to make out the existence of chromatic 

 elements apart from the nucleoli. The appearance in the dory is shown in 

 Figs. 12, 14, PI. III., the former of which represents the germinal vesicle of 

 the egg shown in Fig. 11, magnified 260 diameters. It will be observed that 

 the nucleoli are for the most part peripheral, and that in the central part of 

 the germinal vesicle there are numerous minute spherules or granules, 

 not quite so deeply stained as the nucleoli, and arranged more or less in a 

 chain-like series. This condition is found in the germinal vesicle of all 

 the eggs of this size in the section, but the serial arrangement is not always 

 so well seen. In some cases a minute nucleolus exists in the same region, 

 distinguishable from the granules only by its greater size and refrangi- 

 bility. These eggs of the dory were still evidently far from maturity. 



The condition is still better seen in the large opaque eggs of the 

 angler just before the change at maturation. The appearance of the 

 germinal vesicle in the smaller eggs, which are devoid of yolk, is 

 shown in Fig. 6, PI. III., as seen under Zeiss 2mm. oil-immersion 

 lens, with compensating ocular 4. In the large opaque eggs the 

 nucleoli begin to gather towards the centre of the germinal vesicle, 

 and they are then markedly compound, consisting of aggregations of 

 bright granules, somewhat resembling in optical appearance the yolk- 

 spherules in Zeus faher (Fig. 5, PI. III.). From this preparation, and from 

 another of the nearly mature egg (Fig. 4, PI. III.), to be described later, 

 it would appear that the nucleoli, towards the close of ovarian growth, 

 disintegrate, the numerous minute granules contained within them being 

 set free. A nucleolus which has undergone this change is represented at 

 a in Fig. 5. Compared with the other nucleoli it is very slightly stained; 

 it is flaccid in appearance, devoid of granulation, and with an irregular 

 aperture or cavity ; it strongly suggests a husk or capsule. In the 



