248 MR. 8. LE M. MOORE’S STUDIES 
A third experiment was made for the express purpose of 
ascertaining whether a fallacy might not reside in the above. 
Seeing that Dutrochet found the stream to be stopped by a little 
over three weeks’ darkness at the most, it is highly probable, if 
not certain, that in the specimens used above some slowing had 
been effected in a month. Alterations in the speed of the cur- 
rent. are introduced, as Dutrochet has shown, by shocks; it 
seemed possible, therefore, that the shock experienced by the 
specimen hurriedly brought into contact with the glass slide 
might diminish the speed of rotation. Accordingly the pre- 
caution was now taken of shutting in the dark for several minutes 
prior to examination the glass slide upon which the specimen had 
been placed. 
The piece of Chara vulgaris was removed to darkness on Sep- 
tember 15th, and on October 30th, after the treatment just 
mentioned (the temperature of the room being 62° F., of the dark 
chamber 6175 F.), on the first observation the diameter of the 
field was traversed in an average of 21 seconds; 2 minutes after 
only 16 seconds were required ; 2 minutes after that 14 seconds ; 
after another 2 minutes the space was moved over in 18 seconds, 
and in 11:6 seconds 5 minutes after the last determination. The 
specimen was now thoroughly irrigated with water at 61^ F., the 
intensity of the light remaining constant; and 5 minutes after- 
wards the speed had slowed somewhat, the diameter of the field 
being now traversed in 13 seconds. Frequent applications of 
water at 61? F. followed, the effect being to prevent any slight 
change of temperature, to which alone the slowing just men- 
tioned was to be attributed. Five minutes after this was done 
the normal rate was re-established, the field being passed over in 
11:5 seconds; and this rate was maintained until the close of 
the experiment. 
Thus we see from Table No. III. that although there was a 
difference of less than 1° between the temperature of the room 
and that of the cupboard, yet five minutes after exposure to light 
the stream was moving at nearly three times its former rate, and 
at four times ten minutes after. It is impossible to ascribe the 
whole of this increase to the slight difference in temperature 
between the room and the cupboard; and Table No. IV. plainly 
bears this out. Here, although there was no discrepancy of tem- 
perature, after only five mintues in light the rate of the current 
howed no less than four-fold acceleration. It is submitted that, 
