THE CROWN ANIMALCULE. 
43 
surface of the contractile bladder, and seem to me to ramify over 
it, entering it by many mouths. One of those accidents which we 
can never command or control, but which are often highly instruc- 
tive, gave me a little insight into the nature of the termination 
of these vessels. Examining a specimen of Monocerca porcellus 
which I had killed by means of the compressorium, the sudden 
and strong pressure severed the tortuous respiratory tubes and 
forced them out of the shell (lorica) hanging from the head-mass. 
They now appeared like crumpled cords, covered with close 
transverse lines, probably the effect of corrugation in contract- 
ing ; and from their posterior regions many short lateral 
branches lucre given off, the extremities of which had evidently 
been forcibly torn from their attachments. I have never seen any 
tendency to a trumpet-like expansion of the posterior extre- 
mities of the tubes, at their entrance into the bladder, as 
Leydig implies, nor can I call this latter organ “ a dilated state 
of the united ends of the two respiratory canals,” even in Ste- 
phanoceros. Small as it is in this species it appears to be of the 
normal structure. 
The most remarkable part of the whole apparatus, however, 
is the series of minute tremulous bodies which are attached to 
the respiratory tubes, much like the tags of rolled paper which 
are tied on to the pendent tail-string of a boy’s kite. In all 
the larger Rotifera the watchful eye catches, from time to 
time, a tiny object that has a wavering motion, hke the flicker- 
ing of a flame. Often it cannot be detected at all ; often one 
only, or two such objects are caught ; but in favourable condi - 
tious we may generally discern four on each side (in Asplanchnci 
Briyhtwellii more than a dozen) attached to each tube. 
Ehrenberg was more happy in the function he ascribed to 
these minute organs, than in his physiological nomenclature 
generally. He says, “ Their function is respiratory, and they 
are analogous to gills : the tremulous motion observable is that 
of the lamince composing them.” Here, however, he was 
misled by the deficiency of his instrument, and spoke too 
confidently from mere conjecture. Their structure is not 
laminated. They are evidently little ovate, or pear-shaped 
vessels, seated by a short foot-stalk on the respiratory tube 
and projecting into the body cavity so freely, that they are 
swayed hither and thither by every movement of the fluid 
with which the body is filled. The flickering motion is 
seen to be produced by a single cilium, which occupies 
the interior of the little tag, running through its centre 
lengthwise, attached near its free end, and pointing down- 
ward to its base. A rapid waving movement is communicated 
to the cilium, which is at pleasure intermitted; and so it 
is quite common to see only one or two tags flickering at 
