Feb. 24, 1870 | 
NATURE 
425 
logical unit, simply because this was of old also assumed 
to be the vital unit, we must not allow such mere con- 
fusion in language to confuse us as to the real facts and 
inferences. 
There is another point of view, also, to which Mr. Stir- 
ling does not seem to have given an adequate attention. 
’ The old doctrine did well enough at a time when the 
lowest known living things were “ unicellular organisms,” 
closely approximating in their characters to those morpho- 
logical units of which the higher plants and animals are 
built up. But, since our knowledge has increased—since 
we have become more familiar with the various living 
things constituting the lowest groups of Professor 
Haeckel’s third organic kiigdom—PROTISTA—the main- 
tenance of such doctrines has become im possible. Do 
we not now know that although the Profop/asta are 
amoeboid animals possessing the old cell characters—that 
is, having a distinct nucleus, and a definite bounding 
membrane—there are, nevertheless, adult animals, leading 
an entirely independent existence, composing the lowest 
group JZonera, some of which have no bounding membrane, 
though they have a nucleus, whilst others, simpler still, 
are mere bits of protoplasm—naked, non-nucleated, 
structureless? Yet, such minute, homogeneous, and alto- 
gether indefinite bits of protoplasm, are as capable of 
displaying the fundamental characteristics of life, as are 
the more definite unicellular organisms to which such 
attributes were formerly supposed to be restricted. 
Without visible structure, they nevertheless assimilate 
materials from their environment, and grow; they constantly 
vary their shape, and are capable of executing slow move- 
ments; though possessing no nucleus, they are able to 
divide and reproduce their kind. 
It seems only fair to mention in this place, that so 
far back as 1853, before the doctrine as to the constitu- 
tion of the “cell” had undergone such a modification, or 
rather, as we should have said, before it had been gene- 
rally acknowledged that vital manifestations could be 
displayed by mere bits of protoplasm lacking the supposed 
necessary elements of /ovz, Professor Huxley had put 
forth a powerful remonstrance against the then all-preva- 
lent “cell theory” of organisation.* His ‘opinions were 
announced even five years before Virchow, the last great 
champion of the doctrine, issued his celebrated “ Cellular 
Pathologie.” Following, in the main, the doctrine of 
Wolff and Von Baer, Prof. Huxley contended that the 
primitive organic substance is a homogeneous plasma, in 
which a certain differentiation takes place, but that there 
is no evidence whatever to show that the molecular forces 
of this living matter (“vital forces” of most modern 
writers) are, by this differentiation, localised in any one part 
rather than in any other part—be it cell, or be it intercel- 
lular tissue. “ Neither is there any evidence,” he says, 
“that any alteration or other influence is exercised by the 
one over the other ; the changes which each subsequently 
undergoes—though they are in harmony—having no causal 
connection with one another, but each proceeding, as it 
would seem, in accordance with the general determining 
laws of the organism.” Whilst believing that the fev7- 
plast—corresponding with the cell-wall and intercellular 
tissue of other writers—is the seat of all the most im- 
portant metamorphic processes out of which the various 
* Brit. and For. Med. Chir. Review, 1853, p. 306. 
tissues are produced, he also believes that this differen- 
tiation is not brought about by any mysterious action on the 
part of the cell or nucleus, but that it is rather the result 
of intimate solecu/ar changes taking place in the plastic 
matter itself, after a definitely successive though inexpli- 
cable fashion. Prof. Huxley’s fundamental position was, 
in fact, that “the primary differentiation is not a weces- 
sary preliminary to further organisation—that the cells 
are not machines by which alone further development can 
take place ; they are rather mere indications of accustomed 
modes of evolution.” This main position he has further 
illustrated by saying: “We have tried to show that 
they [the cells] are not instruments, but indications— 
that they are no more the producers of the vital phenomena 
than the shells scattered in orderly lines along the sea- 
beach, are the instruments by which the gravitative force 
of the moon acts upon the ocean. Like these, the cell 
only marks where the vital tides have been, and how they 
have acted.” 
Certainly the essence of this doctrine is, that the 
vital forces are “molecular forces”—that they are not 
dependent upon morphological forms or “cells” and, there- 
fore, that essentially vital manifestations may take place 
in mere formless living matter—Protoplasm, if you will. 
As we have just seen, this is precisely the doctrine to 
which so many other distinguished biologists have now 
given in their adhesion. They too—Max Schultze, Haeckel, 
Kihne, and others—have gradually recognised that a 
something of definite form is no longer necessary : that 
there are independent living things, even lower in the 
scale than the old “unicellular organisims”: that to 
constitute one of these, or to constitute a vital unit 
of one of the higher living things, all that is needed 
is mere formless, indefinite Protoplasm—or, as Mr. 
Stirling contemptuously expresses it, a mere “shred” 
of the matter of Life. 
Much of what immediately follows, in Mr. Stirling’s 
essay, we consider to be somewhat irrelevant. We think 
it has been written under the influence of a misconcep- 
tion as to Professor Huxley’s real meaning. Mr. Stirling 
argues against Protoplasm, on the assumption of its being 
a substance definite in kind—as definite, we may say, as 
chloride of sodium—whilst apparently, Professor Huxley’s 
meaning was rather that Protoplasm was the name of a 
genus of matter, or else of a species including almost in- 
numerable varieties: that it was a proteinacious sub- 
stance, in fact, of which there might be as many hundreds 
of isomeric modifications, as there are similar varieties of 
protein itself. 
We regret that we are unable to follow Mr. Stirling 
into this second part of his essay. It seems to us to be 
the most interesting part of it, and we recommend our 
readers to study it for themselves. Much, however, of its 
reasoning, is, for us, deprived of its seeming cogency, be- 
cause we cannot agree with Mr. Stirling in his previous con- 
clusion as to the non-existence of a matter of Life. This,as 
he fully admits, is the really fundamental question about 
which the difference of opinion exists. And, if we cannot 
agree with him upon this first point, it is useless for us to 
follow him into his subsequent reasonings. We cannot, 
however, but admire his candour when he says : 
It is to be acknowledged . . . that Mr. Huxley would be very 
much assisted in his identification of differences, were but the 
