Protoplasm in Coenocytic Hyphae . 499 
through the centre of a long vacuole, as this lightens the 
friction at the sides (Fig. 3). 
In fact I cannot see in the variety of catastrophes which 
overtake the moving vacuoles any ground of support for the 
supposed autonomy of the vacuoles and a special vacuolar 
membrane, advocated byDe Vries 1 , Went 2 , Wakker 3 , Bokorny 4 
and others. These theories appear to me to be little in accord 
with the phenomena that attend the streaming in coenocytes, 
while much can be seen to favour the views of Pfefif er 5 , 
Btitschli 6 and others, who appeal to the laws govern ing 
viscous fluids in which surface tension assumes an important 
r 61 e. But my observations have not been sufficiently intimate 
and complete to warrant me in pursuing this phase of the 
subject. 
A requirement of the first importance for the display of 
movement, as I have said, is an atmosphere heavily charged 
with moisture. 
Unless extra vasated drops are plentifully scattered over the 
hyphae, movement is not likely to occur. It will probably 
be interesting to describe an instance of their origin and 
subsequent behaviour as seen under a Zeiss microscope with 
D objective and No. 4 ocular (Woodcut 11). The culture was 
on nutrient gelatin with Rhizopus elegans. A filament lying 
in contact with the substratum and showing vigorous stream- 
ing was traced to the growing apex, and found to project into 
the air. The proximal half of the aerial part was plentifully 
supplied with drops. The distal part was free from drops. 
The observations began at 4 p.m., and twenty minutes after- 
wards drops began to appear at some distance apart. These 
grew larger, and intermediate ones appeared. At 5 o’clock 
branches began to protrude through the larger drops. In 
half an hour the branches had grown quite long, and they 
1 Pringsh. Jahr. f. wiss, Bot. xvi, 463. 1885. 
2 Ibid, xix, 295. 1888. 8 Ibid, xix, 423. 1888. 
4 Biolog. Centr. xiii, 271. 1893. 
5 Abh. d.» Sachs. Ges. d. Wiss. xvi, 185. 1890. 
6 Investigations on Protoplasm, 227. 1894. (German text 1892.) 
