32 
Proceedings >of the Royal Society 
An india-rubber ball is pierced by two or three holes near 
together ; these should be about the diameter of a common darning 
needle. A larger aperture (half-an-inch across) is then made in the 
ball, but opposite to the smaller holes, and the ball half-filled with 
white of egg (unboiled) tinted with magenta. The ball represents 
the stroma, while the white of egg takes the place of the inter- 
stromal matter. The ball is now dipped into a beaker of water to 
which sugar has been previously added, until its specific gravity is 
equal to that of white of egg. Place a finger over the aperture 
through which the ball was filled, and press upon it with the other 
fingers of the same hand. Beautiful little magenta-stained pseudo- 
podia will be projected from the small apertures into the sugar 
solution, and on relaxing the pressure, still keeping the finger over 
the aperture above, the pseudopodia will be completely retracted. 
I have been able in this way to project them three or four 
inches, and afterwards they have been completely retracted (the 
experiment was thus successfully performed in the Society’s 
rooms). 
One might use common water in place of the sugar solution, but 
as the specific gravity of the white of egg is greater than that of 
the water, the jaseudopodia, when they have been projected more 
than an inch or so, break off and fall to the bottom. The size 
of the aperture is also rather a nice point, for there is one 
size — roughly q^th inch in diameter — which is best suited for the 
white of egg, although any sized aperture will answer, though 
not so well. This no doubt varies with the fluid used ^—-ordinary 
ink may be substituted for the white of egg, and oil for the sugar 
solution. 
I cannot but believe, that in the stroma the active cause for these 
movements is to be sought for, and, as far as I can see, it must act 
in one or other of the two ways described above, of which I think 
the last is least in antagonism to known facts. 
While, no doubt, many of the bulgings seen in the white corpuscle 
of the newt’s blood are due to changes in shape of the whole cell, 
probably with slight local accumulation of interstromal matter ; 
yet may it not be that many of those fine hyaline processes are 
but interstromal matter projected from the ceil? 
