357 
Centrifugal Force tipon the Cell. 
of life, and to understand the relation of these activities 
of the cell to each other and to the surrounding conditions. 
It does not matter whether these activities be of the so-called 
normal or abnormal kind ; for who is prepared to say what 
is normal and what abnormal, and where the one leaves off 
and the other begins ? 
In this investigation centrifugal force was regarded largely 
as a stimulus, and the purpose constantly kept in view was 
to know what responses the living substance of the various 
cells would make to such a stimulus. 
One of the most surprising phenomena, to the writer at 
least, is the great amount of what seemed to be severe treat- 
ment which many cells are able to endure. In Cladophora and 
various other Algae, where almost every visible trace of the 
living substance save the hautschicht (and the plasmic lamella 
in Cladophora ) is crowded into a small compact mass in one 
end of the cell, and where three weeks or even a longer time 
is necessary to effect a redistribution of these contents 
similar to that existing under ordinary circumstances, not the 
slightest pathological phenomenon could be perceived in 
the vast majority of cases. Aside from the power of mere 
endurance in this respect, the factors that underlie the 
slow or rapid redistribution are still far from a satisfactory 
elucidation. 
Of far greater interest, to the cytologist at least, are 
probably the principles underlying the various, phenomena 
revealed in the types of cell- division which occur in Cladophora 
and Spirogyra. In the former not only does the formation 
of transverse cell-walls not stand in any direct connexion 
with nuclear division, but, so far as known, it is independent 
of the position or distribution of the nuclei. On the other 
hand, it is not improbable that further investigation will show 
that some direct relation does exist between the transverse 
septum in process of formation and the orientation of the 
nuclei. The process of the formation of a cell-wall in the 
cell-division of Spirogyra is in a measure transitional between 
the Cladophora type and that in which the cell-plate is laid 
B b 
