In any case the spindle which projects into the prominence on the surface of the egg divides into two parts, one in the prominence and one in the egg (fig. 26). The prominence itself with the enclosed portion of the spindle becomes constricted off from the egg to form a body, well known to embryologists as the polar body or cell (fig. 27). Since more than one polar cell is formed, that which is the earliest to appear may be called the first polar cell. [FIG. 28. PORTION OF THE OVUM OF ASTERIAS GLACIALIS IMMEDIATELY AFTER THE FORMATION OF THE SECOND POLAR CELL. PICRIC ACID PREPARATION (copied from Fol).] The part of the spindle which remains in the egg becomes directly converted into a second spindle by the elongation of its fibres, without passing through a typical nuclear condition. A second polar cell next becomes formed in the same manner as the first (fig. 28), and the portion of the spindle remaining in the egg becomes converted into two or three clear vesicles (fig. 29), which soon unite to form a single nucleus (fig. 30). The new nucleus which is clearly derived from part of the original germinal vesicle is called the female pronucleus, for reasons which will appear in the sequel. [FIG. 29. PORTION OF THE OVUM OF ASTERIAS GLACIALIS AFTER THE FORMATION OF THE SECOND POLAR CELL, SHEWING THE PART OF THE SPINDLE REMAINING IN THE OVUM BECOMING CONVERTED INTO TWO CLEAR VESICLES. PICRIC ACID PREPARATION (copied from Fol).] The two polar cells appear to be situated between two membranes, the outer of which is very delicate, and only distinct where it covers the polar cells, while the inner one is thicker and becomes, after impregnation, more distinct, and then forms what Fol speaks of as the vitelline membrane. It is clear, as Hertwig has pointed out, that the polar bodies originate by a regular process of cell division and have the value of cells. A peculiar phenomenon makes its appearance in the eggs of Clepsine shortly after the formation of the polar cells, which has been spoken of by Whitman (No. 100) as the formation of the polar rings. The following is his description of the occurrence. "Fifteen minutes after the elimination of the polar globules (_i.e._ cells) a ring-like depression or constriction appears in the yolk around the oral pole, and in this depression a transparent liquid substance (nuclear?) is collected forming the first polar ring.... The same phenomena repeat themselves later at the aboral pole.... The rings concentrate to form two discs.... Before the first cleavage both discs plunge deep into the egg." The nature of these rings is at present quite obscure. [FIG. 30. OVUM OF ASTERIAS GLACIALIS WITH THE TWO POLAR CELLS AND THE FEMALE PRONUCLEUS SURROUNDED BY RADIAL STRIÆ, AS SEEN IN THE LIVING EGG (copied from Fol).]