274 Seifriz . — Observations on some Physical Properties of 
delimits such £ naked ’ masses of protoplasm is also to be found as a cover- 
ing of the cell protoplast lining the cellulose walls of plant cells. 
Having eliminated the true and readily visible membranes (fertiliza- 
tion membranes, pellicles of certain Protozoa, &c.) as not closely comparable 
with the plasma-membrane, we may proceed further to discard one or two 
suggested conceptions of the protoplasmic membrane. Biitschli’s alveolar 
layer has been referred to as a possible plasmatic membrane. I do not regard 
this as a correct interpretation. The alveolar layer is merely a palisade 
arrangement of the superficial alveoli. This arrangement can hardly give 
to the layer any decided special properties not possessed by the alveolar 
protoplasm within. 
It has also been suggested that possibly the hyaloplasmic border of 
myxomycetes, and likewise the ectosarc of Amoeba , is the plasma-membrane, 
or, at least, functions as the differentially permeable layer. Pfeffer ( 29 , 
p. 123) has advanced this possibility. This may hold true in permeability 
phenomena, where not only the hyaloplasmic layer but the entire living 
colloidal system may perhaps function osmotically, but, as I have reiterated, 
it is not with permeability that I am concerned. Microdissection evidence 
indicates the presence of a delicate layer of protoplasm external to and 
more or less distinct from the peripheral hyaloplasm. 
Chambers apparently inclines towards the suggestion of Pfeffer that 
the ectoplasmic layer is the protoplasmic membrane, and does not definitely 
acknowledge the occurrence of a plasma-membrane such as I have just 
described, i. e. a delicate layer more or less distinct from the ectoplasmic 
border. Chambers’s expressions for what might be construed as a plasma- 
membrane are ‘ surface film ’ and ‘ surface layer and the latter he makes 
synonymous with ectoplasm (8, p. 4 ; 9 , p. 11). Only when the ectoplasm 
becomes an exceedingly thin layer, as in ‘ naked ’ marine ova, is it then 
even loosely comparable to a plasma-membrane. Chambers’s ‘ surface 
layer’ is not, even when thin, strictly a film or membrane (although he (11, 
p. 46) occasionally uses the word membrane), for he recognizes no line of 
demarcation between the surface layer and the inner plasm. The surface 
layer, as viewed by Chambers, is a region which ‘ merges insensibly ’ into 
the cell interior ( 11 , p. 45). Pfeffer expresses the possibility of this when 
he says that the more dense layer of the hyaloplasm is ‘ probably only an 
outer zone’ ( 29 , p. 123), and ‘A definite delimitation of the plasma- 
membrane from the inner layers of hyaloplasm is not probable ’, unless 
a more thorough knowledge of the structure of the hyaloplasmic border 
should permit such an interpretation ( 29 , p. 124). 
With this knowledge of some of the many divergent conceptions of the 
plasma-membrane we are better prepared to interpret the following data : 
The Living Membrane . If the hyaloplasmic border of a plasmodium 
which is in the active stage — that is, if it is or has recently been streaming — 
