346 BULLETIN OF THE 



In spindle-shaped cells of the cornea (rabbit) a fine line which traverses 

 transversely the space between the two incipient nuclei {op. cit., Taf. XX. 

 Fig. l.d) is thought to be an indication of the coming cell division. It 

 may, then, I would add, correspond to Strasburger's cell-plate. Similar 

 changes accompany the division of other cells, and are very conspicuous 

 in the frog's cornea. In the Descemet's cells of the latter the fibrous 

 mass is sometimes divided at once so as to give rise to four new nuclei, 

 perhaps in some cases to six or seven. 



The conclusions drawn by Eberth are, to epitomize : — Many cells do 

 not divide simply, but first undergo a metamorphosis which begins with 

 an enlarging of the cell and its nucleus. The latter, by absorption of 

 fluid from the cell protoplasm and by diff'erentiation into clear fluid 

 (Saft), lustrous granules and filaments, becomes lighter. The granules 

 are not derived from the nucleoli, however much they resemble them, 

 for the two coexist. The nuclear membrane is dissolved, but neverthe- 

 less a mingling of the nuclear matter with the protoplasm does not take 

 place. Since the granules and filaments often appear before the dis- 

 solution of the membrane, a complete karyolysis (Auerbach) does not 

 take place. The fibres and granules form a jagged, or globular body, 

 or a spindle figure, whereupon the fibres usually take a regular meridional 

 course, but may remain quite irregular. In the latter case a more 

 regular arrangement is only apparent after the beginning of the divis- 

 ion, which takes place as above described. The fibrous mass, which has 

 arisen in the mother nucleus, is the new nucleus, and gives rise by 

 division to two (or sometimes four or more) daughter nuclei. The 

 mother nucleus, in some cases at any rate, is still present in the later 

 stages of metamorphosis, and is converted into the substance of the 

 daughter nuclei. 



The principal points of difference in the changes of corneal cells as 

 compared with plant cells (Strasburger) are : — The differentiation does 

 not (cornea) begin with longitudinal streakings, but at once with 

 the appearance of the equatorial granules and filaments, which furnish, 

 if not always the whole, certainly a great part of the material for the 

 new nuclei. In the young, cup-shaped, homogeneous nucleus reappears 

 later a differentiation into clear fluid and anastomosing filaments, which 

 latter then undergo a granular disintegration or are changed into a net 

 of fine " Balkchen " and thus form the stroma of a new nucleus. There- 

 by the nucleus appears granular. It then increases in size at the 

 expense of the substance of the old nucleus, whose fluid is probably 

 absorbed by the young reticular nucleus. In the corneal epithelium of 



