42 
POPULAR SCIENCE REVIEW. 
In Stephanoceros there is a rather small but clear bladder, 
(pi. iii.) placed behind the rectum, the filling of which I have 
repeatedly seen, but have never been able to catch clearly the 
contraction. Not that there is any doubt about the process, but 
I beheve the animal invariably retracts its entire body at the 
moment of the systole, so that the process cannot be perceived 
in the confusion. 
In connection with this curious organ there are others equally 
remarkable. Two bands are seen passing along longitudinally 
through the entire length of the trunk, one on each side, in 
most of the Rotifera.* They, for the most part, consist of 
threads, apparently tubular, hanging somewhat loosely, so as to 
form bends, which are invested with a thick corrugated envelope. 
Sometimes the tube forsakes the enveloping matter and passes 
straight along, while the coating forms a great bight. In some 
cases only one of these tubes can be seen on each side, but in 
others two, or even four, can be distinctly traced, loosely twisted 
together. The corrugated coating seems to consist largely of 
fatty matter, and may be intended for the protection of the deli- 
cate tubes. It is particularly copious in Stephanoceros (pi. iii.) 
These organs, which are called by pretty uniform agreement 
respiratory tubes, have never been satisfactorily traced to their 
anterior termination.'! 
Posteriorly, the extremities of the two tubes converge to the 
* They are excellently-well seen in Asplanclina , in Notommata clavulata, 
in N. aurita, in Euchlanis, and in Brachionus. 
t Professor Huxley, describing them in Lacinularia, says, on this point, 
“ Arrived at .the level of the pharyngeal bulb [ mastax ] each vessel divides into 
three branches : one passes over the pharynx [buccal funnel ] and in front of 
the pharyngeal bulb, and unites imji its fellow on the opposite side, while the 
other two pass, one inwards and the other outwards, in the space between 
the two layers of the trochal disc, and then terminate as cceca. Besides these, 
there sometimes seemed to be another branch just below the pancreatic 
sacs.” Possibly some of these apparent branchings may have been only 
threads of connective tissue, whose purpose is to fasten the tubes to the walls 
of the abdominal cavity. I have never been able to trace any coalescence of 
the anterior extremities of these organs in any species. In Brachionus I am 
quite satisfied that each vessel terminates (whether by an open or closed end I 
do not know) in the lining-membrane of the lorica close to the lateral frontal 
spine ; for the vigorous retractations of the moveable head-mass do not at all 
affect the relative positions of these vessels, nor throw them into curves. In 
Eucldanis, on the other hand, they terminate in the head-mass itself, and are 
not attached to the lorica. In Stephanoceros I have sometimes thought that 
there was such a connexion of the vessels as Mr. Huxley speaks of ; for the 
curious little tremulous bags (which I shall presently describe) are found 
chiefly in the region of the neck, arranged around the second collar, but I 
have not been able to detect their attachment. I have seen five at once on 
this level, which seems inexplicable on the supposition of the supporting 
vessels passing only longitudinally on each side. I saw another tag on the 
dorsal side, a little below this level, and (in another individual) two at one 
level near the bottom of the stomach. (PI. iii.) 
