NOTOMMATAD A. 15 
Genus ALBERTIA, Dujardin. 
[GEN. CH. Body vermiform, lengthened ; ciliated face sub-prone ; eyes wanting ; 
jaws minute, forcipate ; foot small, one-toed. Entozoically parasitic in Annellida.— 
iP HG] 
A. INTRUSOR, Gosse, sp. nov. 
(Pl. XVII. fig. 13.) 
[SP. CH. Body greatly lengthened, nearly cylindric, but swollen behind ; foot of 
one joint, besides the toe, which is a small cone ; viscera divided by annular constric- 
tions, within the straight (wnconstricted) integument. 
This species seems distinct from the A. vermiculus of M. Dujardin, if I may 
judge from his figures (Infus. Pl. 22.14, 8). The general form of that is uniformly 
cylindrical, slightly tapering to a great conical foot ; of this, cylindrical, gradually swelling 
to the ventricose hind parts, where a very minute conical toe terminates a small one- 
jointed foot. The mastax and jaws of that species are moderately large; of this, 
excessively minute. That species is parasitic within earthworms and slugs; this, within 
water-worms (Nais). The discovery of the following species makes it almost certain 
that these differences are specific. 
The body is greatly elongated, slender in front, thickening behind the middle, so 
that the diameter of the hind part is just double that of the fore. As, however, a great 
ovate egg was mature im the ovary, at the very extremity of the visceral cavity, of the 
specimen figured, the body may have been more than usually swollen. The ciliated 
face is broad and oblique; the mastax minute, displaying a forcipate incus, with broad 
blades, resembling those of Diglena, to which are attached slender simple mallei, with 
long straight arms inflexed at their extremities. All the trophi are frequently pro- 
truded fully half-way from the ciliated front, and vigorously snapped. A very slender 
cesophagus leads to a long alimentary canal, which is constricted at short intervals 
throughout, but appears to be simple. No gastric, or biliary (?) glands were seen. The 
ovary is long, and occupies the greater part of the abdomen. In all the specimens that I 
examined, there were seyen or eight amorphous nuclei, and one large well-matured ovum 
fillmg up the posterior end; its substance minutely granular, with a vitelline globule 
near the anterior end. Between this ovum and the intestine was a small contractile 
vesicle. A minute point projects from the front, which may possibly be a sense-organ, 
but I perceived no sete on it. A long pointed occipital sac descends far below the 
mastax, but is destitute of any eye-speck. The whole animal is slightly tinged with 
yellow ; and this is the only trace of colour in it, as the abdomen contains no coloured 
food, owing to its peculiar economy. Tor the animal lives as a parasite in the visceral 
cavity of Nais proboscidea. I was examining a specimen of this aquatic worm (in 
October 1854), when a slight pressure of the compressorium caused it to separate into 
t~ parts. I had looked over it with a lens, but had no suspicion that my Nais was 
any other than a single integer, and unfortunately it was not in focus when the separa- 
tion took place, so that I did not actually watch the process. The next moment, how- 
ever, I found that I had two perfect Naides ; the one which had been the tail differing 
only by being a little smaller, but with a head, eyes, and proboscis, as perfect as the 
other. The one which must be called the parent had the hind extremity less distinct 
than the daughter, and there was a slight trace of jaggedness visible. But my attention 
was arrested by a vermiform animal shooting swiftly through the water; and presently 
another. They were evidently Rotiferous, and as I was sure that they had not been in 
the live-box before, I conjectured that they had been discharged from the body of the 
Nais, at the moment of division. This was immediately confirmed : for, on examining 
the Nais, I found, within the alimentary canal of the parent, near the dividing point, 
three or more of the parasites snugly nestled, and actively writhing about. All the 
