C . 8tricklani) 
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mitotic changes but it was not the incompleteness of my description 
which he appears to criticise. 
I contend, however, that the narrative which I gave is correct with 
regard to these points. 
The structure of the Icaryosome in the young trophozoite. 
I say this is a close-wound skein, because I have seen it. Moreover, 
the older trophozoites, Lewin admits, have a band-like karyosome, and 
it is reasonable in itself to suppose that this band is derived from a pre¬ 
existing band rather than from a globule of chromatin. Lewin’s figure 
of a section cut through a young karyosome may perhaps be considered 
to have resulted from distortion, and that it is no thinner than an 
optical section of the entire karyosome. 
The presence of chromatin in the spherules. 
I admit that sometimes the spherules become distinctly blue after 
staining with Haidenhain, but only rarely. It is not, however, the rich 
deep blue that chromatin takes on, but looks rather like a weak “ solution” 
of the stain. Moreover, Romanowsky stains did not give at any time 
a chromatin reaction although Lewin says “it seems probable (sic). . . 
when they contain chromatin they may stain purple” [i.e. the chromatin 
reaction). Lewin admits that finally the spherules lose all their 
“chromatin.” My own experience has been that they never hold 
chromatin in the sense that the karyosome does. It is surely not 
unreasonable to find chromatin in the spherules when it can be discerned 
in the sporozoites. 
The disappearance of the nucleus. 
I stated that the nucleus in the cyst completely disappeared, and as 
far as the membrane and spherules are concerned Lewin agrees with 
me, but his sections show some karvolvmph and patches of (?) chromatin 
remaining. In the first place it is difficult to see how the karyolymph 
remains when the membrane goes, and I think it fair to assume that 
ultimately it also disappears. Secondly, certain of Lewin’s results 
have shown that the impoverished trophonucleus retains a very small 
amount of faintly staining chromatin (the remains of the karyosome 
25—2 
