142 Proceedings of the Royal Physical Society. 
the organs essential for maintaining an individual, and as 
these organs can elaborate food independently of the presence 
of the corresponding organs in the other four arms, it is not 
difficult to see why one arm may continue to live. Why 
it forms four other arms is, however, a question I cannot, 
as yet, attempt to answer. 
Hydra and Begonia, for reasons similar to those advanced 
for the Starfish, are, on being cut into fragments, capable of 
giving rise to several individuals ; provided that each of these 
contains all the tissue elements, and that, in addition, each be 
protected by a certain bulk from detrimental environmental 
conditions; which latter may overcome a small aggregation of 
cells more readily than a large one. 
Such an organism, allowing of a division of the mother- 
individuum into a number of daughter-individua, may be 
said to be built up of “potential” individuals. Hach 
“potential” individual being an aggregation of cells that would 
be able, under normal environmental conditions, to survive 
and to give rise to an individual like the mother :—and this 
latter might be termed a “real” or “actual” individuum. 
Such “ potential” individuals inherit the characters of the 
actual or “real” individual; by receiving all the tissue 
elements of the latter. It is different, however, when an 
individuum propagates itself on its own account. 
A Metazoon consisting of three cells, which differ in their 
functions (Anc+ABc+ABC), cannot reproduce its kind by 
budding off a single cell, for the bud would have to be 
derived from a cell, in which division of labour has produced 
the special development of an organ, and such a cell, if really 
budded off, could not perform its physiological functions 
under ordinary environmental conditions. Theoretically, 
such a bud could only live if it lost the special function 
acquired by its mother-cell—or if the environment was 
changed. That such a Metazoon could give rise to a non- 
specialised bud by a modified process of cell-division, is, 
I think, impossible. 
As long as a special function is bound up in the organs of 
a single cell, the latter cannot give rise to a new or real 
individual; but if the same function be performed by a 
