OVARY AND OVAKIAN OVA IN CERTAIN MARINM FISHES. 129 



material preserved in a mixture coutaiuing -^-^ percent, chromic 

 acid and 40 per cent, picric acid. The condition of the yolk 

 in the three largest eggs is the effect of the picric acid^ which 

 destroys the original form of the yolk globules, and in sections 

 prepared with this reagent the vitellus usually exhibits the 

 laminated appearance shown in the figure. But it generally 

 happens that when the yolk in the larger eggs is well pre- 

 served, the young protoplasmic eggs are shrunken and dis- 

 torted, and vice versa. In one of the younger eggs there 

 are seen two very distinct vitelline nuclei or corpuscles. The 

 sections were treated with the triple stain recommended by 

 Flemming — gentian violet, safranin, and orange G, — and the 

 vitelline nuclei are brightly coloured with the safranin, while 

 the remaining parts show only a light tinge derived from the 

 orange. The vitelline nuclei are round, and differ from those 

 seen in the ova of Pleuronectes in their sharpness of contour. 

 Their outline is very definite, and appears to have no connec- 

 tion with the surrounding cytoplasm. 



The ovum in which the two vitelline nuclei are seen is 

 •16 mm. in diameter. Although the presence of two of these 

 bodies in one ovum is not uncommon, it is more usual to find 

 only one, and there can be little doubt that the presence of 

 two is due to the division of a single one. In the examination 

 of fresh material, treated with acetic acid, I have sometimes 

 seen three, and even four of these bodies ; but when there are 

 several they are proportionally smaller than when only one is 

 present. The earliest condition in which I have been able to 

 demonstrate the structure is, as in other cases, that in which 

 it is in contact with the outer surface of the membrane of the 

 germinal vesicle. Fig. 23 shows the smallest ovum in the 

 section represented in fig. 22 more highly magnified. The 

 greatest diameter of this ovum is 'OlO mm. The vitelline 

 nucleus is seen as a little, hemispherical, highly-stained body 

 attached to the membrane of the germinal vesicle; around it 

 is a region of denser cytoplasm. It may be remarked that 

 even if it should prove that the vitelline nucleus is derived 

 from the germinal vesicle, it is evidently not of the same com- 



VOL. 40, PART 1. — NEW SEE. I 



