566 REPORT—1905. 
a more or less homogeneous interfilar substance. In 1890 Altmans propounded 
his interesting hypothesis that all living substance is made up of minute granules 
or bioblasts, which are the real vital units or elementary organism, embedded in a 
homogeneous substance, the non-living matter. Cells are formed by a combination 
of these units of a lower order, and are therefore individuals or units of the 
second order. 
' At about the same time Butschli brought forward his celebrated hypothesis 
of the froth or alveolar structure of cytoplasm. This was based upon an 
extensive series of observations upon both living and dead cells as well as upon 
froths or foams made by mixing salts of various kinds with oil and then placing 
small particles of the oily mixtures so obtained in water. 
Butschli compares the structure of cytoplasm to that of a fine froth, and con- 
siders that much of the granular, and network or fibrillar structure can be referred 
to the optical appearances presented by such a froth. That such structures are 
visible cannot be doubted by anyone who has examined these froths attentively 
with the microscope. But that all the fibrillar structures described by Fromman 
and Flemming, whose observations have often been confirmed since by competent 
cytologists, can be referred to a froth structure, cannot, I think, be accepted by 
anyone who has carefully examined plant cells. 
The microscopical examination of oil-foams is likely to be of great service to 
us in the interpretation of the appearances seen in the living cell. A fine oil-foam, 
for example, two or three layers of alveoli in thickness, looks exactly like a piece 
of granular cytoplasm such as is often seen in cells. Myen when examined under 
the highest powers, the appearance presented is that of a delicate network filled 
with bright refringent granules more or less regularly spaced, exactly like the 
granular network so often seen in fixed and stained cells. And yet, as Butschli 
has shown, there are no granules in the oil-foam; the granular appearance is due 
to the optical appearance of the meshes above or below those that are in focus. 
So it may be in cytoplasm : much of the granvlar structure we see in it, especially 
when acted upon by reagents or heat, may be due in some measure to the optical 
appearance of minute alveoli. There are, of course, granular structures in the 
cytoplasm which have a very real existence, as can be proved by their movements 
and by their reactions to stains and reagents of various kinds. But staining can- 
not be taken as a proof of the existence of granules. If an oil-foam be stained by 
osmic acid we get an appearance of a brownish network containing deeply stained 
(black) granules, although when a layer only one layer of alveoli in thickness is 
examined no granules can be seen. It seems to me, therefore, that we have to be 
extremely careful in our interpretation of structure of protoplasm, especially as 
seen under high powers of the microscope. It is possible that many of the dis- 
crepancies in the accounts given of both cytoplasmic and nuclear structures may 
tend to disappear if attention be paid to such possibilities as those which are 
revealed in a careful investigation of oil-foams. 
Butschli’s hypothesis has received a considerable measure of support owing to 
the ease with which the appearances described by him can be seen, especially in 
cells at-certain stages of development. Butschli considers that the fine froth-like 
structure is not to be confounded with the coarser vacuolar structure which is 
often found. Whether sucha difference exists between the coarser vacuolar 
structure and the fine alveolate structure seems to nie difficult to determine. 
IY have examined some hundreds of different kinds of plant cells, both 
living and in the fixed and stained conditions, and I have never been able to 
convince myself that there is any essential difference between them. We can easily 
see, as Wilson has described for animal cells, under favourable conditions, a dis- 
tinct gradation from the minute alveolate structure, described by Butschli, through 
all intermediate stages up to the coarser vacuolation of the cytoplasm. And the 
same is also true of oil-foams. So also we can trace the alveolate structure in 
cytoplasm from the minute alveoli down to smaller and smaller alveoli, until at 
Jast an alveolar structure is no longer visible, even under the highest powers and 
best illumination which are at present possible. We then get a perfectly homo- 
geneous appearance in the cytoplasm, just as in fresh white of egg. 
