286 
Pr.ocmlings of the Royal Society 
The lowest amceboid organisms are simply granular masses of 
protoplasm, but higher forms exhibit a differentiation of a hyaline 
zone of “ ectoplasm ” around a more fluid and granular “ endoplasm/’ 
The immense variability of form, size, and general appearance pre- 
sent among the rhizopods has never been sufficiently allowed for ; 
so that there is ample reason for doubting whether great numbers of 
described species have any real distinctness. Yet the elongated 
and reticulated, granular and circulating pseudopodia of the Fora- 
minifera, and the radiating, clear, and far less contractile pseudo- 
podia of the Heliozoa and Eadiolaria present a most vivid contrast, 
which we have as yet no means of explaining. The remarkable 
changes presented by ova both before and during fertilisation,* 
and the doubtless fundamentally similar phenomena exhibited 
during cell division, require to be accounted for; while the long 
dispute as to whether the “ granules ” of protoplasm are really 
granules at all, or are the optical expression of the intersections of a 
stroma or network of denser protoplasm, cannot be omitted. Such 
a hypothesis must also aim at throwing light upon the mystery of 
muscular structure, and must also deal even with such apparently 
peculiar and exceptional phenomena as that “aggregation of the proto- 
plasm,” first described by Mr Darwin as occurring in certain cells of 
insectivorous plants f (which, when in active digestion, or when 
subjected to chemical, electrical, or even mechanical stimuli, exhibit 
an aggregation, or rather segregation of the protoplasm into two 
portions — the outer more or less hyaline, but containing irregular 
and constantly-changing streaks and granules of a more refracting 
and fluid substance, in which the colouring matter, when present, 
became accumulated). 
2. Statement of the Hypothesis . — Darwin soon extended these 
observations to the protoplasm of root hairs, and went on to indicate 
its wide prevalence throughout the vegetable kingdom. His re- 
searches were verified and extended by Francis Darwin, J who 
showed that these granules did not consist of sap, as some vegetable 
histologists had suggested, but were essentially protoplasmic in their 
nature. It is the object of the present paper to apply these facts to 
* Balfour, Embryology, vol. i. 
f Darwin, InsectivoroiLS Plants, London, 1875. 
X Quart. Jour. Micros. Science, xvi. 
