Notices of Irish Entozoa. 575 



often greatly elongated, compressed on each side, very nar- 

 row, truncated anteriorly, or terminated by a tumid margin, 

 projecting on each side ; at other times inversely conical, be- 

 ing very broad in front, and flattish above and below ; more 

 rarely sub-orbiculate, or ovate, acute anteriorly, carinated in 

 the centre, but otherwise flat on both sides. Fovea marginal, 

 oblong, or nearly obovate, and deep. Neck none. Body flat, 

 its margin crenate. Joints, those nearest the head for the 

 most part very long, very narrow, and nearly wedge-shaped ; 

 the posterior margin on each side a little prominent, but of- 

 ten, especially after the animal is dead, contracted, and ap- 

 pearing scarcely longer than the others. The joints next to 

 these shorter and gradually broader, the posterior joints near- 

 ly equal, mostly square, and for the most part broader than 

 long, and sometimes composed as it were of two or three amal- 

 gamated together. Ultimate joint obtuse. 



A longitudinal line runs on each side through the larger ar- 

 ticulations, and in the space bounded by these the reproduc- 

 tive organs are placed, the joints on the dorsal surface exhi- 

 biting an orbicular, simple or double nodule, of a whitish, 

 brown, or blackish colour ; in like manner, on the ventral 

 surface, a simple or double, but less prominent nodule is pla- 

 ced, and which appears to be perforated ; and the body being 

 pellucid, a central but generally irregular line arises from the 

 presence of the nodules. The latter being open are continu- 

 ous with the ovaries, and are filled with moderately sized el- 

 liptical ova, which are often also effused around them.* 



Rudolphi farther observes that this species, when recent, 

 is generally entirely white, but after being immersed for some 

 hours or a day or two in water, the ovaries of the larger arti- 

 culations become brown or blackish, which colour they after- 

 wards retain in spirits. This change he supposes to depend 

 on a certain state of the ovaries, as it does not take place in 

 every specimen. I have observed this change of colour much 

 more remarkable in specimens from the Cottus than in those 

 from the brill or turbot ; and as I have generally found the 

 Entozoon more developed in the former fish than in the two 

 latter, I would conjecture that the more mature the ova, the 

 more certainly would the change take place. I have seen 

 specimens originally almost quite white, exhibit on every pos- 

 terior joint, after lying a night in water, a spot of a line in di- 

 ameter, and as black as ink. 



The frequent change of shape in the head adverted to above, 

 is caused by the efforts of the animal to move forwards. Tn 



•Rudolphi, ' Entoz. Hist. Nat' vol. ii. part 2, pp. 51, 52. 

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