” 
164 GILBERT ©. BOURNE. 
the second proposition is an assumption which is made to 
explain the first. We may make Mr. Sedgwick a present of 
the last three, whilst we retain and value the first. 
The essence of the whole question is this: are we justified 
in considering the elementary parts of an organism to be 
independent life units? Before we can answer this, we must 
inquire why we do consider them to be independent life units? 
The answer to this is probably to be found in the aphorism, 
which commends itself to everybody, that reproduction is 
discontinuous growth. From the observation that, in 
unicellular organisms, division of the unit—the cell-corpuscle 
—leads to the liberation of a new and independent unit, and 
that in multicellular organisms it is the liberation of an 
independent unit—the ovum—which constitutes reproduction, 
it has become a settled conviction in men’s minds, that division 
of a cell-corpuscle means the liberation of a new unit, that is, 
the setting free of a new independent being. It is this con- 
viction which has led to the belief that the units composing a 
multicellular organism are in posse independent beings, 
though in esse subordinate to the whole of which they form 
a part. This was the argument of Schwann when he wrote 
the passage which I have quoted on p. 149, and the argument 
has been taken as conclusive. 
But we know now that the power which Schwann and his 
followers limited to cells is inherent in protoplasmic masses 
not divided into cells. For instance, if the cell-membrane 
of a Celoblastic alga is ruptured, portions of the exuded 
protoplasm, provided they contain one or more nuclei, may 
become, after a time, surrounded by a new cell-membrane, 
grow, and form a new plant. 
The experiments of Gruber show also, that portions of 
Amecebe artifically separated may, provided that they contain 
nuclear substance, recover from the operation, and lead an 
independent existence. 
May I ask, in parenthesis, whether there can be a better 
illustration of the truth of the contention which I have en- 
deavoured to establish above, that whilst a uninucleate cor- 
