in ike Pollen- Mother-Cells of Larix. 301 
figure appears, we must assume either that the many centro- 
somes have now fused into relatively few, or that the one has 
passed from the nucleus out into the cytoplasm and there has 
divided into ten, twelve, fifteen, or twenty. It seems evident 
from such considerations that the assumption of the possible 
presence of organs like the animal centrosome in the cells in 
question involves an ignoring of the best-established facts. 
The impression is given by a study of the arrangements 
and rearrangements of the kinoplasm that the activities con- 
cerned in the formation of the spindle centre in, or have 
reference to, the nucleus. Such an impression led Nemec 
(’98 b) to the hypothesis that the nucleus, in cells without 
a centrosome, is ‘ homo-dynamic 5 with the centrosome where 
it occurs. It is true that the ultimate function of the fibres, 
in the completed spindle, has reference to certain nuclear 
constituents — the chromosomes. From the generally accepted 
notion of the nucleus as the bearer of hereditary qualities, it 
follows, too, that that organ is the ultimate source of the 
stimuli which determine the synthetic processes of the cell ; 
and this hypothesis is borne out by a considerable mass of 
experimental evidence (Wilson, ’00 ; Gerassimow, ’01 ; &c.). 
It is quite possible, therefore, to suppose that the ultimate 
directive agencies for the growth and even for the arrangement 
of the kinoplasm, as of other cell-constituents, may finally 
be traced to the nucleus. But this is very different from 
saying that the present seat of the energy which is manifested 
in the movement of a particular fibre is within the nucleus ; 
and it seems to me that the facts which we have been con- 
sidering are inexplicable on the basis of the latter assumption. 
It might be imagined that the nucleus, acting like an immense 
centrosphere, should produce some such system of rays as 
appears in Fig. 6 ; but that it should, by exerting an influence 
at all comparable to the supposed action of a central body, 
be directly concerned in the metamorphosis of the early 
reticulum into a radial system, or in developing from the 
latter a felt, a multipolar or a bipolar spindle, seems quite 
inconceivable. 
