190) CELL AND NUCLEAR DIVISION IN FULIGO VARIANS 237 
it has meanwhile become multinucleated. It would seem that 
differentiation was dependent to a certain degree, at least,on the 
interaction of individualized protoplasmic units, each capable of 
receiving and reacting to independent stimuli as the parts of a 
multinucleated cell cannot. Hertwig, in his doctrine of biogen- 
esis, himself insists on the importance of the interaction of 
separate cells for the production of physiological differentiation 
and division of labor. 
o be sure, we have abundant evidence that the multinu- 
cleated cell can achieve a certain degree of differentiation, as is 
shown in the numerous Siphoneze which mimic in their root- 
like, leaf-like, and stem-like structures, the analogous parts of 
the higher plants. It is perfectly apparent, however, that this 
differentiation is on a far simpler scale than is seen in the com- 
plex mechanical and other tissue systems and organs of the 
higher plants, Indeed, the relative unimportance of the Sipho- 
hee as a part of the earth’s vegetation is to be regarded as very 
strong evidence that the type of structure which they show in 
their multinucleated cells is by no means well adapted to develop 
“omplexity and differentiation of structure such as is necessary 
es meet the manifold variations in environmental conditions to 
Which all plants are subjected. Thesé Siphonez are after all 
a more differentiated than the infusorians, which are typi- 
: y unicellular, _ Pfeffer (16) puts the case very strongly when 
in Sp ee that we can conceive of no such independent units 
multinucleated cell as the energids of Sachs are defined to 
egy energid is a nucleus with a portion of cytoplasm 
the Somes control, there can be no such structures in 
pionee, since the protoplasm of their cells is constantly 
i one point to another, with the exception of the 
hin. ee : a which remains fixed. No nucleus could thus 
Di . nite relations with any particular portion of the 
int heise, Neg and it is hard to conceive that in this stream- 
- CONstantly ; ‘3 Portion of the semifluid cytoplasm should remain 
Says, w YM connection with any particular nucleus. As Pfeffer 
_ ome must conclude that any specific mass of cytoplasm in a 
