THE ‘NON-CELLULAR’ TYPE 51 
simplicity, is furnished by the seaweed known 
as Caulerpa Stahlii. As is shown by the 
annexed illustration, the plant consists of 
a creeping stem from which arise the erect 
leafy expansions; while the whole is anchored 
by root-like structures which penetrate, or 
adhere to, the substratum. In spite of this 
high degree of external differentiation, there 
is no internal partitioning, and no one of the 
vast number of nucleated protoplasts, which 
together make up the living substance, is 
segregated physically from its neighbours by 
obvious boundaries. But there is one signifi- 
cant and interesting feature about the dis- 
tribution of the nuclei in the protoplasm. 
They are crowded at the growing points, 
and are more widely spaced asunder in the 
older regions. In this apparently trivial 
circumstance we can discern exactly the 
same arrangement as would have been ob- 
served had the partitioning walls been actually 
present, for the dividing cells in the growing 
points always appear to be both numerous 
and small, owing, of course, to the rapid 
cell division which is going on in such regions. 
Now this “ non-cellular ” or “syncytial” 
(see p. 21) type of organisation entails 
certain obvious disadvantages on its possessor, 
but we find that in some instances the at- 
tendant risks have been overcome in a 
wonderful way. On coral reefs and similar 
calcareous stations an alga known as Halimeda 
Opuntia is sometimes found (Fig. 8). It resem- 
