NOTOJIMATAD^. 15 



Genus ALBERTIA, Dujurdin. 



[GEN. CH. Body venniform, lengthened; ciliated t&ce sub-prone ; eyes xc anting ; 

 jaws minute, forcipate ; foot small, one-toed. Entozoically parasitic in Ajinellida. — 

 P.H.G.] 



A. INTKUSOE, Gosse, sp. nov. 

 (PL XVII. fig. 13.) 



[SP. CH. Body greatly lengthened, nearly cylindric, hut sivollen behind ; foot of 

 one joi7it, besides the toe, which is a small cone ; viscera divided by annular constric- 

 tions, xvithin the straight (unconstricted) integument. 



This species seems distinct from the A. vermiculus of M. Dujardin, if I may 

 judge from his figures (Infus. PI. 22. 1 A, b). The general form of that is uniformly 

 eylmdrical, 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 mmute. Tltat species is parasitic within earthworms and slugs ; this, within 

 water-worms {Na'is). 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 in 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 

 (Esophagus 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 seven or eight amorphous nuclei, and one large well-matured ovum 

 filling 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 setfe on it. A long pointed occipital sac descends far below the 

 mastax, but is destitute of any eye-§peck. 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. For the animal lives as a parasite in the visceral 

 cavity of Nais proboscidea. I was examining a specimen of this aquatic worm (in 

 Dctober 1854), when a slight pressure of the compressorium caused it to separate into 

 t" J 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 Naidcs ; 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 hmd 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 



