5° 
Walter Stiles 
oogonia, egg cells and embryos of Fucus, Spirogyra, Vaucheria , 
Rhizopus and Zygorhynchus, pollen tubes of Iris versicolor, Lathy- 
rus mariiimus, Erythronium revolutum, protozoa, and ova of 
Echinoarachnius, finds the viscosity of protoplasm varies greatly in 
the different cells examined. Young Fucus oogonia and embryos 
and the streaming protoplasm of Myxomycetes were the most liquid, 
the mature and resting eggs of marine organisms were the most 
viscous. This author however is of opinion (1920) that great caution 
should be exercised in using viscosity as the only criterion of a sol 
or gel condition of the protoplasm. 
Price decides that in resting spores, for example, those of Mucor, 
the protoplasm is in the gel condition, but that on germination it 
becomes a sol. Changes in the consistency of Fucus eggs during 
maturation and fertilization are described by Seifriz (1918), while 
the same writer (1920) states that as a myxomycete prepares to 
fruit the protoplasm increases in viscosity until it becomes in con¬ 
sistency a gel. Seifriz has observed such changes in protoplasmic 
viscosity which are reversible. “The viscosity of protoplasm is not 
fixed, for it varies in different organisms, in the same organism at 
different times, and even in different regions of the same organism 
at the same time” (Seifriz, 1920). 
Thus even where the bulk of the cytoplasm is a sol there is a 
considerable quantity of evidence that the surface layers of the 
cell plasm may be in the more solid gel condition. Loeb (1906) 
says confidently: “It is a general rule that every free cell is sur¬ 
rounded by a solid film.” He instances as evidence of this the length 
of the pseudopodia of rhizopods, which is so great that if the pseudo¬ 
podia were entirely liquid they would fall apart into droplets. As 
protoplasmic streaming takes place in the interior, the solid part of 
the pseudopodia must be at the surface. Ramsden (1894, 1903) and 
Traube (1867) have shown the formation of solid membranes at 
the surface of hydrosols. 
In cells in which Chambers decides the cytoplasm is in the sol 
condition he finds the peripheral layer very dense in consistency 
as compared with the interior of the cell, the outer layer merging 
insensibly into the general body of the cytoplasm. This surface 
layer is particularly well marked in protozoa, for example, in 
Paramoecium. Chambers concludes that the surface layer is a 
“highly extensile contractile and viscous gel,” which if damaged 
may be automatically repaired. In adult somatic cells where the 
interior cytoplasm is judged to be in the gel state it is not possible 
