198 
$ 7. Here is discussed, that there are yet two other 
phenomena, which might give information about the place 
of the isoëlectric point, namely the sticking to the glass 
and the mutual sticking together of the algae with their 
cilia. The first phenomenon, however, took place in 
solutions, which were more acid than those, in which the 
plasmcolloïds, according to the course of the curves are 
isoëlectric. This is attributed to the negative charge of 
the glass with regard to alkaline, neutral and very weakly 
acid solutions. 
In which solutions the mutual sticking together took 
place, was not noted down. Besides the fact that in the 
sticking to the glass the influence of the charge of the 
boundary surface glass water plays a part, a removal of. 
the phenomena to more acid solutions can be expected in 
all cases in which the motility of the algae is very great. 
Under the influence of the light or of gravity the algae 
come continually with the cilia into contact with the glass, 
by which loss or taking up of electrical charge can 
take place. 
We point to the fact that the acid optimum of Chla- 
mydomonas with chemotactical experiments is perhaps an 
acid optimum only under the influence of the glass. 
