36 J. T. CUNNINGHAM. 



results were gained by colouring fresh eggs on the slide 

 with saffranin or some aniline dye, and then adding acetic 

 acid, or by using the compound acetic acid carmine, after 

 Schneider's method. Sometimes Flemming found that the 

 acetic acid carmine gave a better vStaining when the ova 

 had previously been treated with nitric acid of 40 or 50 per 

 cent, strength, and then carefully washed with distilled 

 water. 



Concerning the main features of the process of karyohi- 

 nesis there is a striking similarity in the descriptions of the 

 numerous observers, although the objects of observation 

 differ so widely, but there is great variety of opinion as to 

 the details. Some of the discrepancies will probably vanish 

 witli increase of knowledge, but the process doubtlessly 

 varies to some extent with the character of the cell. 



Flemmiiig's Typical Case. — According to Flemming,* who 

 took for the chief material of his careful researches the tissues 

 of Salamandra, the changes w^hich take place in the indirect 

 division of a cell are those represented in figs. 1 — 15. The 

 nucleus in its resting state is enclosed by a membrane which, 

 in optical section, shows a double contour (fig. 1). Within 

 the membrane is a " reticulum " or framework (Geriist) of 

 fibrils, a homogeneous ground substance, one or more nucleoli, 

 and in some cases a few smaller granules. Flemming believes 

 the nucleoli to be connected with the fibrils of the reticulum, 

 and denies that there are any independent granules ; but the 

 majority of investigators speak of nucleoli and granules 

 lying free in the ground substance. In the resting nucleus 

 all the elements are stained by dyes — the membrane, the 

 nucleoli, the fibrils, and the ground substance. When the 

 nucleus is about to divide the membrane disappears, toge- 

 ther Avith the nucleoli and all granules and thickenings of 

 the fibrils. The mass of fibrils loses its reticular character 

 through the disappearance of the nodal points, which Klein 

 and Flemming believe to be in great part the cause of the 

 granular character so often ascribed to nuclei. There are 

 no free ends of fibrils to be seen, but an appearance such as 

 would be presented by long endless fibrils bent irregularly 

 in all directions. This stage is called by Klein^ that of the 

 " convolution," which seems to be the only short equivalent 

 in English of the expressive German word " Knauel." In 

 this and all succeeding stages of the metamorphosis only the 

 fibrils are affected by dyes ; the ground substance remains 

 transparent, and round the mass of fibrils is a clear space 



1 ' Virchow's Archiv/ Bd. 11, 1879. 

 = 'Atlas of Histology,' 18S0. 



