THE CROWN ANIMALCULE. 
45 
the intestine, to form the “ cbylaqueous fluid” of Dr. Williams, 
— the analogue of blood in the superior races. The effete 
water is then directed through the tags by their open ends, the 
vibrations of the inclosed cilium imparting the inward current 
to it, and so into the bladder. I quite believe this to be the 
true state of things ; and therefore, that the respiratory tubes 
represent the kidneys, and that the bladder is a true urinary 
bladder. Thus in Insects, with which class I consider the 
Rotifeea most closely allied, the kidneys exist in the form 
of long, often tortuous tubes, generally from four to eight in 
number, and often those of each side twisted loosely together, 
in which uric acid has actually been detected ; while in some, 
as the water-beetles ( Dijticidce ), there is a voluminous urinary 
bladder. 
If this explanation be according to fact, it follows that the 
respiratory and urinary functions are in the closest relation 
with each other. 
The Nervous System. — The nervous matter in this class 
exists in a remarkably concentrated and conspicuous form, 
constituting’ a cerebral mass, which, for its proportionate 
volume, may compare with the brain of the highest Yerte- 
brata. One is amazed to find such an organ in the lowest 
type of the Articulata, so compact, so well-defined, so large ; 
and it is not without considerable hesitancy that we are induced 
to admit its right to a cerebral character. Yet there can be no 
reasonable doubt, that such it is. Its position in the anterior 
region of the animal, and usually with a dorsal aspect ; its 
rounded outline, and compact figure ; its greyish, granular 
texture ; and, in particular, the connection with it of the eye, 
which is invariably seated like a wart upon it, — reveal its true 
character, which, so far as I know, has not been questioned by 
any observer. 
Ley dig does not recognize the brain in Stepltanoceros ;* yet 
I find it clear and indubitable, though small. (PI. iii.) It is 
placed on the dorsal side, just beneath the second collar, behind 
the upper part of the crop, and immediately beneath the 
* I do not mean that he has not described and figured the organ, but he 
does not recognize its function or homology. Under the title of “ Special 
Organ,” he has these words : “ Immediately over the crop is found a structure, 
the value of which is unknown to me. It is a group of vesicles, clear as water, 
which together form a body ’024 line in diameter, which opens by a short but 
evident passage in the cuticle.” This is certainly the brain. Its position, its 
conformity of structure with the brain in other Rotifera, and the seating of 
the red eye-point on its rotundity, which I have distinctly seen, leave no 
doubt on the point. The orifice he alludes to is paralleled by what I believe 
to be antennal orifices in Asplanchna, and by an actual antenna in Notommata 
clavulata, to which muscular and nervous threads go direct from the brain. 
