A Fountain Alga. 
75 
In July the surface of the pond was clear of plants and weeds 
and light could easily penetrate to the bottom, but later in the 
year a thick felted mass of watercress covered the surface, in suffi¬ 
cient quantity apparently to prevent any light reaching the bottom. 
No difference could, however, be detected in the macroscopic or 
microscopic appearance of the Alga under the changed conditions. 
The first examination of the grains showed that a particular 
species of Alga, coating the grains, is concerned in all cases. 
Owing, however, to the impossibility of studying the detailed 
structure of the Alga on the irregular surface of sand grains, it 
was suggested that an attempt should be made to imitate the 
natural conditions as nearly as possible by means of artificial 
springs in the laboratory. 
The following apparatus was fitted up in the laboratory, and 
by its means the Alga was induced to grow. A large bell-jar was 
inverted and to the narrow neck was fitted a cork, through which 
passed a piece of glass tubing drawn out to a small hole. This 
tubing was connected to a tap and a miniature fountain was thus 
produced. Quantities of sand covered with the Alga were placed 
in this fountain and were kept in motion by the current of 
water, thus imitating to a certain extent the natural conditions. 
It having been shown that the Alga will grow under these condi¬ 
tions, glass coverslips were placed vertically in the the throat of 
the fountain, with one end embedded in the sand grains, the argu¬ 
ment being that if the Alga will grow on silica it will grow on 
glass. 
The Alga grew readily on coverslips, and these, when required, 
could be removed and placed on a culture cell, where the life-history 
of the Alga could be observed. 
The above apparatus was in use for about three months, but 
was found inconvenient for several reasons—the chief one being that 
while the sand grains in the centre were exposed to the current of 
water, those at the sides of the bell-jar were at rest and not bathed 
by fresh quantities of water, and thus the natural conditions were 
not completely imitated. 
A second and improved form of apparatus was then fitted up (Fig. 
74). This consisted of a glazed porcelain trough, on the bottom of 
which was placed a flat spiral of lead composition tubing of £ in. inter¬ 
nal diameter. This spiral was pierced at intervals of about one inch 
with fine holes on the upper side. Both ends of the spiral were 
open and connected by rubber tubing with a tap. The trough was 
