Notes . 
287 
to experiment on protoplasmic movement. They are easily prepared 
by cutting rather thick transverse sections of the corolla, and mounting 
in water. They react quickly to various stimuli, and they possess the 
additional advantage of being readily accessible during the greater 
part of the year. 
I also tried the effect of exposure to an atmosphere of hydrogen on 
Ophrydium versatile , a colonial protozoan consisting of a large number 
of green Vorticella-like animals imbedded in a common gelatinous 
matrix. An exposure to hydrogen for half an hour in bright daylight 
produced no apparent effect, but after continuing the treatment for 
a further quarter of an hour, the large cilia had become sluggish 
in their movement. The experiment was then discontinued. In 
another series, a group of Ophrydia which had been for twenty 
minutes in an atmosphere of hydrogen, but seemed to be still perfectly 
healthy, were covered over with a dark box. After the light had been 
excluded for three minutes, a number of the organisms were found to 
have been killed, and a further exposure to the gas in the dark for 
three minutes resulted in the death of them all. They contracted, 
and quite suddenly burst, the green matter streaming out as globules 
into the water from the glairy mass of the disintegrating body of the 
animal. 
This experiment shows that the utilization of some oxygen-contain- 
ing substance (probably the carbon dioxide evolved during respiration) 
takes place under suitable conditions of illumination, and it may 
probably be concluded that the evolution of oxygen available for 
the continuance of the respiratory process is connected with the 
presence of the green colouring-matter already referred to. But it 
would seem that the balance between the two processes of assimilation 
and respiration, between the evolution and utilization of oxygen, is 
not so accurately maintained in this instance as in that of Elodea ; 
since after three quarters of an hour’s exposure to the atmo- 
sphere of hydrogen, the activity of the animal was clearly waning, 
although the conditions of illumination appeared to be in all respects 
favourable. 
In 1887 Pringsheim published a series of researches on the 
behaviour of Chara in an atmosphere of hydrogen to which a small 
amount of carbon dioxide had been added 1 . Pie states that the 
1 Pringsheim, Ueb. d. Abhangigkeit der Assimilation griiner Zellen von ihrer 
Sauerstoffathmung, &c. Sitzungsber. d. k. Preuss. Akad. d. Wiss. z. Berlin, 
U 2 
