of Edinburgh, Session 1883 - 84 . 
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solution of the old dispute, as to whether the integument of certain 
planarians was amoeboid or ciliated, was afforded by specimens of 
Convoluta which had been kept for many days in a shallow aquarium, 
scantily protected at nights from the cold of a severe winter. 
The normally ciliated cells of the ectoderm could be watched in 
actual progress of collapse into the amoeboid state, and their cilia 
figured during their passage into pseudopodia (fig. 24), Here was 
a definite pathological change, in approximately known conditions, 
and distinctly in terms of the cell-cycle. Why should not a dis- 
order of the ciliated epithelium of the bronchial passages be at least 
partly susceptible of essentially the same explanation 1 (fig. 25). 
May not the formation of pus be partly interpreted in terms of 
degeneration to the amoeboid stage, and may not inflammatory 
changes be regarded as temporary and excessive intensifications of 
cellular activity, indicating a tendency to reversion to the amoeboid 
state ? 
Whether these particular instances be acceptable to professed 
pathologists or not is after all a minor consideration, their aim has 
been merely to suggest that the phenomena of the cell-cycle — 
and particularly of those changes occurring under definite experi- 
mental conditions — may be applicable in their hands to fruitful 
research, not only in pathological histology, but in cellular physi- 
ology and therapeutics.'^ 
Its adaptability to the treatment of physiological speculations is 
also obvious. Since the activities of the body are the aggregate 
activities of its component cells, not merely such phenomena as 
those of varying ciliary activity, but those of fatigue and sleep, 
of muscular and nervous tonus, and in fact every rhythm of increas- 
ing and decreasing cellular activity, become intelligible when viewed 
from this most highly generalised standpoint of physiology, as 
specialisations of that primeval cellular rhythm Which lies before us 
in this life-history of the Protomyxomycete. 
13. Influence of the Emironment upon the origin of Plants and 
Animals . — One further physiological consideration may be briefly 
indicated, from its bearing on general morphology. The cell-cycle 
in its entirety is only possible in a fluid medium. Without water 
cilia cannot play, without fluid the amoeba and the plasmodium must 
* This conception is somewhat developed in the subsequent paper. 
