481 
POPULAR SCIENCE REVIEW. 
repeatedly. Lest, however, you be unsuccessful, I must describe 
to you what takes place. 
If you get a sight of the animal, while fully expanded and 
rotating, sidewise (as shown in fig. b), you will see that the 
front outline of the head descends from the sinus between the 
great upper petals, and follows an irregular curve to a rounded 
projection which I have familiarly called the chin. Below this 
there is a considerable recess, at the bottom of which we may 
discern a tiny cup-like cavity, midway between the two an- 
tennae. I have indicated it (in fig. b) as seen through the 
transparency of the flesh, which projects a little on each side 
of it. 
Carefully marking now the course of the great ciliary wave 
on the margin of the petals, you will observe a certain devia- 
tion from its circular course. But this will be made much 
clearer by an ingenious device, which will afford you pleasure 
on several accounts. Rub a cake of water-colour carmine on a 
palette, and with a sable pencil take up a minute portion, and 
diffuse it in the water of your animalcule cell, which contains 
your Melicerta. Put on the glass cover, and observe again. As 
soon as the little animal recommences its ciliary gyrations, the 
dark-red atoms of pigment are put in motion, and you see at once 
that you have obtained a very important aid in distinguishing 
the currents. If you have not diffused too much paint, the 
animal will continue its rotations without inconvenience, and the 
transparency of the water will not be materially affected. The 
result is immediate and striking. Particles of red pigment are 
drawn from all quarters toward the disk, on approaclung- which 
they arrange themselves in a wide band, which is hurled 
along in directions parallel to the sinuations of the margin, 
keeping a uniform distance just outside the ever-chasing black 
wave-specks. This band of red dots circles ceaselessly round 
and round, but at the great frontal sinus a portion of 
them is ever drawn off from the general course, and driven 
along the irregular front fine, which you see in the side view 
(fig. b), toward the projecting chin. The cloud of dots rapidly 
runs on round the tip of this organ, rushes under it, still fol- 
lowing the outline, till it terminates in the tiny cup beneath, 
which I have already mentioned. In order now to pursue the 
observation with advantage, we must get a sight of the animal 
in front, so as to have a direct view of the little cup. This would 
be by no means a chance scarcely to be hoped for, for while 
the Melicerta is engaged in building she very frequently turns 
herself from side to side, so as to bring different aspects of her 
person before the eye. Having’ obtained such an aspect, you 
see that the interior of the little cup is beset with very minute 
cilia, which maintain a rapid rotation. The frontal current. 
