An ordinary meroblastic ovum consists then of a small disc at the formative pole, known as the germinal disc, composed mainly of protoplasm in which comparatively little food-yolk is present. This graduates into the remainder of the ovum, being separated from it by a more or less sharp line. This remainder of the ovum, which almost always forms the major part, usually consists of numerous yolk-spherules, embedded in a very scanty protoplasmic matrix. In some cases, _e.g._ the eggs of Elasmobranchii[46], the protoplasm is present in the form of a delicate network; in other and perhaps the majority of cases, too little protoplasm is present to be detected, or the protoplasm may even be completely absent. In some Osseous Fishes, _e.g._ Lota, the yolk forms a homogeneous transparent albuminoid substance containing a large globule at the pole furthest removed from the germinal disc. In this case the germinal disc is sharply separated from the yolk. In other Osseous Fishes the separation between the two parts is not so sharp[47]. In these cases we find adjoining the germinal disc a finely granular material containing a large proportion of protoplasm; this graduates into a material with very little protoplasm and numerous yolk-spherules, which is in its turn continuous with an homogeneous albuminoid yolk substance. In Elasmobranchii we find that immediately beneath the germinal disc there is present a finely granular matter, rich in protoplasm, which is continuous with the normal yolk. [46] _Vide_ Schultze, _Archiv. f. mikr. Anat._ Vol. XI.; and F. M. Balfour, _Monograph on the Development of Elasmobranch Fishes_. [47] _Vide_ Klein, _Quart. Journal of Micr. Science_, April, 1876. Bambeke, _Mem. Cour. Acad. Belgique_, 1875. His, _Zeit. für Anat. u. Entwicklung_. Vol. I.