136 
He now changes the method and puts the object into 
the capillary tube, which is filled with distilled water and 
puts this under the cover-glass in a drop which consists 
of the acid-solution. When he states, that a swarmspore 
that will leave the capillary tube makes the ‘motorreflex- 
movement at the month (Kusano points out that his 
object reacts exclusively phobochemotactically like Para- 
maecium) the acid-solution under the cover-glass must 
possess a concentration, which corresponds to the threshold- 
value of that acid. Thus he finds the threshold-value for 
sulphuric acid to be !/,,500 molair, for hydrochloric acid 
1/,5000 molair, for tartaric acid !/2500—*/10000 molair, for 
malic acid 1/,0509—/6000 molair and for acetic acid !/,,6 
molair. Ît is very peculiar how he himself speaks of his 
changed method or rather of the found threshold values: 
,» We cannot yet by all means determine this critical con- 
centration but we will satisfy ourselves in accepting the 
following method, which may give, at least in my case, 
more accurate result for our purpose than by the usual 
capillary method.” 
J, myself, too have tried to get an insight into the 
dimension of the threshold. My experiment-organism was 
Chlamydomonas variabilis Dangeard. It reacts positively 
to all acids, which I have examined (strong inorganic 
acids, phosphoric acid, carbonic acid, acetic acid, malic 
acid). Into the capillary tubes I put, for example, 0,1 
normal acid. Before the mouth of the capillary tube, I 
got a ring-shaped accumilation. In a similar preparation, 
but without the organisms, the water was provided with 
a certain quantity of a methyl-red solution. By this it got 
a rather clear, orange-vellow colour. Under te influence 
of the acid, which diffused from the capillary tube, a red 
ring was formed before the opening of it. The place of 
thing ring coincided almost with the ring, which was 
formed by the organisms in the other preparation. The 
