and their Position in the System of the Annelida. 395 



of the corpuscles is given by Claparede at 0*010 mill. ( = 0-005 

 line) ; I found it to be greater, namely 0-006-0-008 line, or 

 about one-tenth of the length of the shorter uncini. As far as I 

 can remember, those observed in Copenhagen presented a similar 

 proportion, although, from the small size of the animals exa- 

 mined by me (most of them measured only 5 lines), they ap- 

 peared to me to be uncommonly large. The corpuscles flowed, 

 with the fluid of the somatic cavity, from one segment into the 

 other, above and below the ligaments (or dissepiments, as Van 

 Beneden calls them) which fasten the wider portion of the ali- 

 mentary canal to the wall of the body. This occupied by far 

 the longest part of the body, and in a specimen of thirty-three 

 segments (such as most of those examined by me in Copenhagen) 

 extended through sixteen of them, increasing slowly in width 

 towards the middle. The oesophagus, about half the size, 

 usually reached in repose, when it describes one or two curves, 

 into the ninth segment ; the end of the intestinal canal, which, 

 again, is considerably thinner, and lies in short convolutions, 

 usually passed through from four to nine segments; but even 

 in the hindermost part of the wider division of the alimentary 

 canal I detected balls of excrement. In the extremely narrow 

 lumen of the very muscular oesophagus, which is linear in 

 repose, I repeatedly observed ciliary movement. 



The uncini, which stand four or five together on the segments, 

 one or two on the hindermost segments, were moved, as far as I 

 could see, in the same way as the setse, single muscular threads 

 proceeding from the wall to attach themselves to the free end of 

 the bundle which projects into the ventral cavity. Sometimes 

 in one of the bundles of setse, which occur only on the first seven 

 segments (or eight, according to Van Beneden), and also con- 

 tain four or five setae, single setae were replaced by uncini, but 

 only in one, two, or three of the hindermost of them : Van 

 Beneden gives this as the rule. Oersted called my attention to 

 a flat, nearly oval body, running out, as it were, into two lobes, 

 which was discovered by him lying over the buccal cavity, and 

 which he thought to be the superior ganglionic mass of a buccal 

 nervous ring. I regard this interpretation as the more probable 

 because there was on each of the two lobes a well-defined black 

 point, having exactly the appearance of an eye-point. Claparede 

 also notices these points, but adds that he could not detect a 

 lens in them. 



Ova, which I observed in a specimen at Copenhagen, occurred 

 neither in paired sacs repeated in the segments nor in the so- 

 matic cavity, into which they get from these, according to Van 

 Beneden, but in two delicate-walled sacs situated at the sides of 

 the intestine, which commenced at the twelfth segment and 



26* 



