INTRODUCTION. 9 
clusive evidence is forthcoming to show whether this 
substance is permanent in all cells, and whether it was 
originally nuclear or cytoplasmic in origin, although 
the widespread intra-nuclear condition favours the 
view that it originated there.’’* 
The importance of the nucleus in the economy of all 
unicellular organisms has been well established. With- 
out it the function of digestion cannot take place. 
Hofer in 1889, and Verworn later, demonstrated that 
no digestive fluid is prepared in the cytoplasm when 
the nucleus is absent. Hofer also held that the slimy 
secretion by which the common Amba anchors itself 
before food-taking is never formed by the enucleated 
portions ; and Verworn in 1888 showed that enucleated 
pieces of Polystomella (one of the marine Foraminifera) 
could not repair or regenerate the lost shell, while 
nucleated pieces quickly repaired it. The conclusion 
of this observer was that enucleated protoplasmic masses 
cease entirely those chemical processes by which pro- 
ducts of the normal shell are used or formed. The 
generalisation may now, Calkins concludes, be made 
that no secretion takes place in enucleated fragments. 
On the other hand, the nucleus, by itself. e. separated 
from the cytoplasm—has no longer the power to 
regenerate the lost parts, and like the enucleated cyto- 
plasm, soon dies. Biitschli’s conclusion that “ the 
nucleus needs the plasm, the plasm the nucleus,” seems 
well grounded. Their activities are reciprocal. One 
without the other cannot live. The process of secre- 
tion, therefore, whether for the purpose of digestion, 
or whatever else, in the life of the unicellular organism, 
is expressed by constant chemical interchange between 
the cytoplasm and the nucleus. 
Means or Locomorion. 
Except in a small number of species, the Rhizopoda 
are endowed with the power of locomotion through 
* Op. cit., p. 278. 
