282 Seifriz . — Observations on some Physical Properties of 
rather precludes looking upon the vacuole as an autonomous or permanent 
organ. 1 
The behaviour of the contractile vacuole of certain Protozoa, as 
apparently first described by Wrzesniowski (45 and 46 ), to which my 
attention was called by Dr. C. V. Taylor, who has observed the same 
temporary existence of the contractile vacuoles in Euplotes and Paramoecium , 
quite does away with the possibility of looking upon the contractile vacuole 
of Protozoa as a permanent organ, and therefore precludes the existence of 
any sort of permanent protoplasmic membrane surrounding the vacuole. 
It seems ( 45 , p. 162) 2 * that the contractile vacuole in certain Protozoa is 
formed by the fusion of several smaller vacuoles, and on ejection of the 
vacuolar contents to the exterior, a new vacuole is formed by the fusion also 
of several smaller ones, and the formation of the new vacuole may be — 
in fact, usually is — initiated before the complete disappearance of the old 
discharging vacuole. 
The fusion of the vacuoles and the temporary life of the ultimate con- 
tractile vacuole make it difficult to conceive of the vacuole as so intricate an 
apparatus as Stempell ( 39 , p. 458) describes it. But especially does the 
fusion of the vacuoles indicate the temporary and facile character of the 
‘ wall ’. If the vacuolar membrane is at any time a rigid gel, solation 
apparently takes place on the fusion of two vacuoles and also on contraction 
of the ultimate vacuole. 
Thus is the vacuolar membrane, like the peripheral cytoplasmic j 
membrane, essentially protoplasm, fluid in consistency, and if at times it is 
in the gel state then it is readily reversible. 
The Nuclear Membrane. The most beautiful demonstration of a proto- I 
plasmic membrane (using protoplasm in its broadest sense) is to be had by 
dissecting the isolated nucleus of an Amoeba. The nuclear membrane 
is generally believed to be a more definite and more readily distinguishable 
structure than the surface membrane of cytoplasm. This may be true, but 
the nuclear membrane cannot in the living state be any more readily 
distinguished or isolated than can the outer cytoplasmic membrane. 
Kite ( 22 , p. 6) describes the nuclear membrane of the eggs of Asterias, 
Cuminga , &c., in these words: c This structure is a concentrated tough gel of 
relatively high viscosity and is not to be confused with the hypothetical surface 
of vacuolar plasmatic membranes. 5 Chambers ( 9 , p. 10) supports Kite with 
the statement : ‘ Evidence that this membrane is a morphological structure 
is shown on withdrawing some of the nuclear contents with a micropipette. 
1 Arthur (1, p. 499 ), in describing ‘the variety of catastrophes which overtake the moving 
vacuoles ’ in the hyphae of bread-mould, says, ‘ I cannot see . . . any ground of support for the 
supposed autonomy of the vacuoles and a special vacuolar membrane advocated by de Vries, Went, 
Wakker, Bokormy, and others.’ 
2 This resume was taken from the article in Russian by Wrzesniowski (45), but reference is also j 
given (46) to the more extensive work in German. 
