Protoplasm by Aid of Microdissection . 291 
plasm. The ectoplasm nearly always maintains its identity, but the very 
dilute endoplasm frequently mixes with the water when it is exposed by 
a deep rupture. Here is an exception to the general rule stated above, 
namely, that protoplasm is immiscible in water. There are, however, three 
important facts to remember in connexion with this uncommon instance of 
apparently true miscibility of protoplasm : first, the protoplasm which is 
miscible is exceedingly dilute ; second, the mixing of the liquid endoplasm 
with water takes place in only about fifty per cent, of the cases ; and third, 
with miscibility the protoplasm as such is lost. The endoplasm of the 
ciliate infusorium Euplotes, which is the most liquid protoplasm of any 
examined by me. is also frequently miscible in water. Escaped protoplasm 
from pollen tubes is another exception to the general rule that protoplasm 
is immiscible. But here, likewise, the protoplasm is very dilute and mixing 
takes place in only about half the number of cases. 
In examining protoplasm with especial reference to its miscibility in 
water one must not be misled by the miscibility of an abundance of cell sap, 
which is not strictly protoplasm and which occupies so large a part of the 
interior of some plant cells. If one of the large internodal cells of Char a be 
cut in two the contents will flow out and diffuse rapidly in the surrounding 
water, but the by far greater portion of this outflowing substance is cell sap. 
The Chara protoplast consists of two thin layers (the outer quiescent, the 
inner streaming) of protoplasm lining the cell wall, and the bulk of the cell 
content is made up of the vacuolar cell sap. It is this cell sap which mixes 
in the surrounding water, while what little of the protoplasm flows out can 
be seen as small isolated and immiscible clumps scattered about in the water. 
The above experimental facts justify the conclusion that living proto- 
plasm, in the great majority of instances, and in all cases where the living 
substance is normal and above a minimum viscosity, is immiscible in water. 
Whatever our point of view on the water-miscibility of protoplasm, we 
are forced to admit that in most instances it does not mix with water when 
exposed to it. The question now arises, Why is protoplasm usually 
immiscible ? Chambers ( 9 , p. 2), who holds that protoplasm is miscible in 
water, answers this question by saying that the condition of miscibility 
obtains unless a protective membrane or surface layer intervenes. Viewed 
in this light the problem practically becomes non-existent, because in most 
instances a membrane does intervene, and when no membrane intervenes we 
are usually justified, for other reasons than the inability of the protoplasm 
to form a membrane, in assuming the protoplasm to be degenerate. That 
the surface layer is in many respects protective may be reasonably assumed, 
but is not the surface layer protoplasm ? It differs, to be sure, physically, 
and possibly also chemically, from the inner protoplasm, just as the ecto- 
plasm differs from the endoplasm, and the endoplasm on the one side of a cell 
may differ at any moment from the endoplasm on the other side of a cell. 
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