506 Arthur. — The Movement of 
vacuolar sap, which has probably been used in growth or 
extravasated (Fig. 5). 
It has been impossible in this presentation of my studies to 
touch upon a number of questions which have arisen during 
their progress, or to discuss fully those brought forward. 
I have attempted to give as briefly as possible the main 
facts regarding the streaming movement of the contents of 
hyphae where the coenocytic structure furnishes an uninter- 
rupted passage of considerable length. The passage is usually 
some millimetres, and often many centimetres, in length, and 
often equals one-fourth millimetre, or even one-half millimetre, 
in diameter. I have brought together a number of observa- 
tions which seem to me to clearly indicate that the movement 
is in the main a physical one, dependent upon osmotic condi- 
tions ; although there can be little question that lying back 
of the physical factors the living protoplasm functions as 
a strong inciting and controlling agent. I have found, in 
fact, although not before mentioned, that streaming can be 
set up in a purely artificial manner that does not differ in any 
observable particular from the natural streaming. In a culture 
of Rhizopus nigricans , the application of a drop of a 20 per 
cent, solution of potassium nitrate caused a vigorous move- 
ment for a time through the hyphae toward the place of 
application. It is evident that this plasmolytic agent ex- 
tracted the water from the filaments, thus causing the flow. 
After a time normal conditions prevailed in the hyphae 
experimented with. A T5 per cent, solution produced but 
slight movement. I need not recapitulate the conditions 
which, under normal relations, effect the plasmolytic changes. 
I have observed the streaming movement in the following 
eight species of Mucoraceae : Mucor Mncedo , L. ; M. race - 
mosus , Fries ; Rhizopus nigricans , Ehr. ; R. elegans (Eidam), 
Ber. and De T. ; Phycomyces nitens (Ag.), Kze. ; Sporodinia 
Aspergillus (Scop ), Schrot. ; Thamnidium elegans , Lk. ; and 
Pilobolus crystallinus (Wigg.), Tode. I do not doubt but 
that it occurs normally in many other coenocytic forms, where 
the conditions are favourable. 
