SUMMARY. 
Chapter [I 
$ 1. The way in which one works when studying 
chemotactical phenomena is compared to the proceeding 
for the examination of phototropical and geotropical 
processes. By this it is possible to call the supposition 
concerning the separated sensibilities for different chemo- 
tactic active substances, premature. 
$ 2. With the help of data from literature is pointed 
out, that the capillary method is not a very suitable one 
to get a closer insight into the nature of the chemotactical 
phenomena. 
$ 3. Here is discussed, that a colloïd-chemical repre- 
sentation can be formed of the influence of chemotactica. 
Ehapter I 
$ 1. It is: denoted how the algae, which served for 
the experiments, were cultivated. By determination was 
proved that the Alga used was Chlamydomonas variabilis. 
$ 2. Here is discussed, that the terms physical process, 
chemical process, physiological process and stimulation 
process are unfit to keep apart the various phenomena 
from physiology. 
8 3. For Chlamydomonas variabilis Dangeard was 
observed a very clear positive geotaxis while it appears 
from literature, that some investigators have found Chla- 
mydomonas pulvisculus to be negativily geotactical. 
Recueil des trav. bot. néerl. Vol. XVII. 1920. 13 
