confiuens and the Morphology of the Ascocarp . 377 
Irritable membrane, and from this standpoint it may be 
one- or many-nucleated. That there is a certain unity in 
a mass of tissue such as a palisade parenchyma made up of 
.cells combined in a leaf for the performance of a definite 
function is not to be questioned, but this unity is achieved by 
the combination of the activities of a number of independent 
co-ordinate individuals. Each cell in the tissue receives its 
own nutrition and throws off its own wastes, and each receives 
and reacts to stimuli from its environment. 
The continuous plasma-membrane enclosing a coenocyte is 
plainly in its relation to the other cell-contents to be compared 
with the same structure in a uninucleated cell rather than with 
the aggregate of membranes, which bound off a mass of tissue 
from its environment, and the cells of the tissue from each 
other. And it is this bounding layer which through its 
properties as a semi-permeable membrane regulates the 
income and outgo and thus the nutrition of the cell, and also, 
according to Noll ( 26 ) at least, determines its reactions to 
external stimuli. 
The sum of the reactions in a mass of tissue-cells may be in 
harmony and serve some common end for the organism, but 
they are none the less independent in origin and in their 
accomplishment in that they are co-ordinated. In the case 
of a multinucleated cell we have no evidence that either the 
process of taking in food or the reception of stimuli is in 
anything different from what it is in the'case of a uninucleated 
cell—except perhaps in the amount of food taken in—the 
multinucleated cell being frequently proportionally larger. 
The motions of a multinucleated plasmodium compared 
with those of a uninucleated amoeba show no indication of 
being compounded from the motions of independent units. 
So far as can be judged from its amoeboid and streaming 
movements the plasmodium is a unit in the same sense as is 
the amoeba. 
Schenk ( 30 ) has presented evidence that the katabolic 
processes by which energy is liberated are functions of proto¬ 
plasm independently of its organization into cells, and that 
