190 W. WALDEYER. 
exception of the spindle, under the name ‘“ Kerngrundsub- 
stanz,”’ and he now sees pari passu a simple division of the 
‘‘Grundsubstanz,” in the form of a constriction, occurring 
together with the kinetic process in the thread figure. He 
therefore comes to the following conclusion : 
1. The nucleus is at all times a perfectly independent struc- 
ture inside the cell. 
2. Karyokinesis is the expression of a process occurring in 
the celJ-nucleus, in which no morphological constituent of the 
cell takes any active part. 
Moreover, Pfitzner concludes that the configuration of the 
nucleoplasm (Kerngrundsubstanz) always closely agrees with 
the chromatic figure, so that he arrives at the supposition that 
the movement of chromatin is primary. 
This statement is in agreement with the opinion of E. 
Zacharias (209) that the delimitation of the nucleus from the 
cell-protoplasm is always distinct. 
Strasburger, too (190, 194), has asserted that between the 
separating halves of the chromatic figure there always remains 
a substance which divides and that part goes to one and 
part to the other daughter-nucleus; but in opposition to 
Pfitzner, he believes in an incursion of the constituents of 
the cell-protoplasm between the thread constituents of the 
nucleus. Again Tang], in a work carried out in Flemming’s 
laboratory (196 a), has lately speken in favour of such an in- 
termixture of the “ interfilarmasse”’ of the cell-substance with 
the nuclear sap during mitosis, and he endeavours to disprove 
the evidence of the preparations made by Pfitzner’s method. 
In his latest memoir (191) Strasburger takes the same 
view, and confirms his earlier assertions, so that consider- 
able doubt as to the correctness of the opinions put forward 
by Pfitzner, Sattler, and myself have been raised. I cannot 
allow this matter to drop, since, undoubtedly, the repeated dis- 
covery of true mitotic nuclear division in Protozoa is very 
important for the whole question. Here, according to the 
united opinion of all students (Biitschh (48), R. Hertwig (94), 
Pfitzner (156), Gruber (82), and especially Schewiakoff (178), 
