Miscellaneous. 141 



contrary, present at one of their poles a little bud, the size of which 

 increases until it becomes equal to that of the maternal cell ; one 

 of the nuclei passes to the interior of the bud, and thenceforward 

 we may recognize two cells, separated from each other by a circular 

 constriction, which deepens gradi;ally ; the two daughter cells be- 

 come individualized, but remain closely connected with each other. 

 The two cells, therefore, are produced by division from a primitive 

 mother cell. I have always found it impossible to distinguish any 

 trace of cell-membrane about these young ovules. 



It is indispensable here to make two observations : — first, that these 

 mother cells occur in great quantity in the ovaries immediately after 

 oviposition, as may be seen from the fact that the ovisacs contain 

 eggs which are still at the first commencement of embryonic deve- 

 lopment ; secondly, that the dimensions of the mother cells are the 

 same as those of the little cells which are found in the form of ah 

 eminence situated at one of the i}oles of the mature egg. All the 

 other characters of the mother cells are identical with those which 

 are presented by these polar cells of the mature eggs. In both we 

 see a perfectly transparent protoplasmic body, holding in suspension 

 some rounded, very refractive globules, and we even find some of 

 considerable size, which present no diff'erence in character from 

 those of the viteUus. We distinguish in them a vesicular nucleus, 

 with very delicate outlines, provided with a nucleolus endowed with 

 considerable refractive power. 



The mother cells of which I have spoken give origin, by means 

 of division, to two daughter cells. At the commencement of their 

 development these cells are all exactly alike. Soon, however, their 

 bulk increases slightly, and each of them acquires by degrees the 

 dimensions of the mother cell. They each contain some refractive 

 globules ; but soon the number of these globules increases greatly 

 in one of the two united cells, and, at the same time, its size begins 

 to exceed that of its congener. From this moment it becomes im- 

 possible to distinguish, in the midst of these refractive globules, the 

 nucleus of the enlarged cell. I have never afterwards succeeded in 

 distinguishing in the mature egg the cell-nucleus in the midst of 

 the vitelline mass. The cell increases more and more ; it completely 

 fills itself with refractive globules, of which the size increases as 

 quickly as the number. Whilst enlarging, this cell (which we may 

 now call the egg, since we recognize distinctly in its contents the 

 characters of a true vitellus) preserves a perfectly regular spheroidal 

 form ; only at one of its poles the second cell, which has remained 

 stationary in its development, is attached. When the egg has at- 

 tained a diameter of from 0'16-0-18 millim. we distinctly recognize 

 in it a cell-membrane, which is developed at the expense of the 

 periphery of the protoplasm of the ovicell, and betrays itself by 

 its dark outline. This membrane (vitelline membrane) is not a 

 common enveloi^e of the enlarged cell (which is the egg in course of 

 development) and of the transparent cell joined to one of its poles ; 

 it does not enclose this latter cell, but, on the contrarj', its contour 

 stops at the margin of the surface of attachment of the egg and the 



