1889.] Psychology. 741 
the scene of action, turning both right and left in search of his hfeless 
prey. This search lasts a minute at the most, after which, if not suc- 
cessful in finding his victim, he starts off once more to the chase and 
resumes his irregular and roving course. 
the two stout vibratile lips with which its mouth is armed, and swal- 
lows them alive and whole. The victims may be seen struggling and 
tossing about for a time in the interior of the Leucophrys's body, and 
afterward to expire slowly under the action of the digestive juices of 
the vacuole in which they have been enclosed. Placed in a medium 
well-stocked with small Ciliates, the Leucophrys have their bodies con- 
stantly crammed with victims swallowed in the manner above described. 
Like the other hunter Ciliates the Leucophrys does not espy its victims 
from a distance, and does not guide itself toward them. It simply 
darts about from right to left, every moment changing its direction. 
It thus increases its chances of coming in collision with its prey, and 
vibratile lips, it is seized, irresistibly drawn toward the mouth and 
swallowed within less than a few seconds. 
"The prehension of food by the Didinium exhibits interesting as- 
pects which have not as yet been observed in any other Infusory. M. 
Balbiani, in his first observations, had often been surprised at seeing 
animalcula that the Didinium had passed by without touching, sud- 
denly stop as if violendy paralyzed ; whereupon our carnivorous speci- 
men straightway approached and seized them with seeming facility. 
More careful examination of the Didinium's actions soon furnished the 
key to this enigma. If, while swifdy turning in the water, the 
Didinium happens in the neighborhood ofananimalculum, say a Para- 
mecium, which it is going to capture, it begins by casting at it a 
quantity of bacillary corpuscles which constitute its pharyngeal arma- 
ture. The Paramecium immediately stops swimming, and shows no 
other sign of vitality than feebly to beat the water with its vibratile 
cilia; on every side of it lie scattered the darts that were used to strike 
it. Its enemy then approaches and quickly thrusts forth from its mouth 
an organ shaped like a tongue, relatively long and resembling a trans- 
parent cylindrical rod ; the free, extended extremity of this rod it 
fastens on some part of the Paramecium's body. The latter is 
then gradually brought near by the recession of this tongue-shaped 
organ toward the buccal aperture of the Didinium, which opens 
wide, assuming the shape of a vast funnel in which the prey is 
swallowed up. 
