Address of the President. 
25 
at the same time, " vacuoles" filled with a more liquid mate- 
rial would appear in the substance of the protoplasm, and 
these would increase and coalesce, until at last the principal 
part of the interior would be occupied by the watery fluid, 
the viscid protoplasm being confined to the layer immediately 
lining the primordial utricle. Further, the secretion from 
the surface, instead of being a soft gelatinous slime, would 
constitute a firm protective envelope, — the cellulose wall. 
Now this is what may be actually seen, in following the evo- 
lution of the " zoospores" of Confervae, &c., into perfect cells ; 
for these zoospores are nothing else than protoplasmic parti- 
cles, formed by the subdivision of the contents of the cell 
from which they are set free, having one or more filamentary 
prolongations, by the vibration of which they are propelled 
through the water ; and it is not until they have fixed them- 
selves, and have begun to grow, that they present any indica- 
tion of that distinction of parts, which I have spoken of as 
characterizing the typical cell. 
There is another phase in the lives, not only of Protophytes, 
but of more highly-organized plants, in which, according to 
recent observations, a most important functional act is per- 
formed by particles of protoplasm not yet furnished with a 
cell-wall. Thus in Vaucheria^ in which the existence of dis- 
tinct sexes, and the performance of a true generative act has 
been substantiated by the admirable observations of Prings- 
heim, it seems very clear that while the contents of the sperm- 
cell are metamorphosed into self-moving antherozoids which 
make their escape from it, those of the germ-cell simply form 
an aggregate spherical mass in its interior, which, at the time 
of the entrance of the antherozoids, has no limitary membrane. 
The antherozoids, coming into contact with its surface, swarm 
over it, and seem to undergo dissolution upon it ; and it is not 
until a fusion has thus been accomplished between the con- 
tents of the sperm-cell and those of the germ-cell, that the 
product of this fusion becomes invested with a definite mem- 
brane, and is thus developed into a cell. The observations of 
Dr. F. Cohn upon the generation of Sphwroplea annulina are 
to precisely the same effect ; and Dr. Pringsheim, carrying out 
more fully the observations of Thuret on the fertilization of 
simply the superficial layer of the protoplasm more condensed than that 
which it encloses. It does not appear to the Author that this constitutes 
a sufficient reason for recognizing it as a definite membrane, where it has 
a membranous consistence. And the controversy will be seen to be one 
of words rather than of things, when the presence or the absence of this 
membrane is viewed as a matter simply depending upon the degree of 
differentiation which the protoplasm may have undergone. 
