406 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Protista, employed the following apparatus. The fluid containing the 
organisms was placed in a rectangular cell, the long sides of whicli, 
composed of porous clay, were from 1-5 mm. thick and 20 mm. long, 
the shorter ends being composed of a cement made of a mixture of 
wax and resin. To the clay sides or electrodes were applied the brush 
electrodes. These were short glass tubes, closed at one end with clay 
and filled with a saturated solution of zinc sulphate. From the plug 
projects outward the brush, while at the other end projects inwards a 
zinc rod connected with the wires. Sometimes the extremities of the 
electrodes were made of porous clay and cemented down to the slide, 
so tbat their points were immersed in the fluid. The current was 
produced from a chromic acid battery of twelve elements, the cells of 
which were 17 cm. high and 11 cm. broad. 
In this way the author found that various species responded dif- 
ferently to the two kinds of stimulus, some being atfected by the positive 
current and others by the negative. 
By the use of the porous points instead of brushes it was found 
that the galvanotropic effect was not confined to a small area near 
the electrodes, but was actively efScient even in vessels of 10 ccm. 
contents over the whole mass of water. Hence the action tended to 
collect the organisms into aggregations. For example, in the same water 
Flagellata would accumulate about the anode, the Ciliata about the 
kathode. 
When the movements of Protista are to be studied to ascertain the 
influence of light, it is important to remove all sources of disturbance. If 
a large drop of water should be used, the Microscope must be quite 
horizontal, oblique light must be cut off by surrounding the slide with 
black paper, and the waiTuing power of the transmitted light obviated by 
the interposition of a layer of ice between the mirror and the slide. The 
Protista may then be examined either by placing them under the Micro- 
scope with all the just-mentioned precautions, and with the addition of 
first coveriug the mirror with black paper. The paper is then suddenly 
withdrawn, and the movements observed. Or a drop of water containing 
the organisms is placed on a cover-glass coated on the other side with 
black paper, in which a window 3 mm. square has been cut. The effect 
of coloured light can be observed by interposing solutions such as 
ammonia, copper, and bichromate of potash. 
The effect of warmth can be studied in a similar way, that is, by 
means of first covering the mirror and observing the movements through 
the window of the cover-glass. It is of course necessary to first ascertain 
the degree of heat by previously focussing the light on a thermometer. 
The effect of mechanical irritation was ascertained by shaking the 
slide either once or frequently. The continued vibration was attained 
by fixing one end of the slide and moving the other end up, and then 
allowing it to drop by means of a toothed wheel of four cm. diameter, 
and with the teeth 1 cm. apart. 
In addition to the foregoing, the effects of local, acoustic and chemical 
irritants were also examined. 
The behaviour of small pieces as compared with uninjured organisms 
was also observed. The pieces were obtained by crushing or cutting 
with a knife made by sharpening a needle intu a blade. 
