K(-) 
<■ 
Fl(4URE 8. 
potential) at the surface forming the physiological anode will 
be diminished, and that at the physiological kathode increas- 
ed ; hence the former surface will diminish owing to the in- 
creased surface tension, and the latter will increase : hence the 
cilium will bend towards the anode, as indicated by the small 
arrow, and the organism will be propelled towards the kathode 
— it will be "negatively galvanotactic." The effect of the same 
current on a 'negative" ciliated organism will, of course, be 
the reverse. Hence, we may formulate the rule that ''positive'' 
organisms will be attracted to the kathode, and "negative^' 
organisms to the anode. When a very strong current is 
passed, the lowering of the surface tension at kathodic points 
in a "positive" organism or at anodic points in a "negative" 
organism may be so excessive that the parts of the surface no 
longer coKvre, and the organism breaks up. This is the ex- 
planation of the disintegration of certain organisms under the 
action of a constant current, e.g., Pelomyxa.* The effect of 
the constant current upon organisms which are neither ''nega- 
tive" nor "positive" — that is, which are equally loaded with 
anions and kations — must obviously be attraction to hoth elec- 
trodes, since a contact P.D. would be artificially produced at 
both surfaces : thus, such organisms would not exhibit any 
marked preference for either electrode. We have now to 
consider the effects of chemical re-agents upon these organisms. 
From the point of view of the theory which I have put 
forward, the phenomena of chemotaxis must be attributed to 
the diffusion of the ions in the re-agents into the protoplasm 
in different proportions. Consider the effect upon a "posi- 
tive" amoeboid cell (A, Fig. 4), of a salt such as KCl, in 
which the kation has a greater velocity than the anion, diffus- 
ing from a capillary (B). Since the quicker-moving kations 
will diffuse faster than the anions, more kations will enter the 
* Yerworn : Geiiieitil Physiology : Trans, by Fredenc S. 
Lee, page 419. 
