History of the Hairy -backed Animalcules. 401 



charged, which, before, as it lay near the extremity of the 

 body, had much puzzled me : it was probably the undissolved 

 envelope of a minute animalcule, which had been devoured. 



In one specimen, a large very clear viscus of irregular 

 form occupied the widest part of the body, above the intestine, 

 elevating the back into a hump. After some hours this viscus, 

 which at first appeared structureless, developed an egg-cell 

 with its nucleus, thus proving to be the ovary. The entire 

 animal is of a pale smoky colour. It does not crawl like the 

 Chaetonotes, but habitually swims swiftly about, keeping, 

 however, near the bottom of the water. 



Fig. 11 represents an individual as it appeared after it 

 had become sluggish, and apparently dying; it is evidently a 

 view lengthwise along the back, the lower part, or that next 

 the observer, being, I believe, the head. It is valuable as 

 showing the arrangement of the angled hairs. 



Sp. 9. D. antenniger (Gosse). (PL ii. Figs. 13, 14.) Hairs 

 short, downy; a pencil of long hairs at each angle of the 

 posterior extremity; head furnished with two club-shaped 

 organs resembling antennee. The horse-pond on Hampstead 

 Heath yielded me this species, in August, 1850. It is a little 

 smaller than the preceding, the length being only 1-1 70th of 

 an inch ; but measured to the tips of the hairs, l-140th. In 

 general figure, and in some particulars of its organization, it 

 appears to diverge less from Ch&tonotus, than the preceding 

 species does. The head is round, as wide as the body; and 

 there is but little constriction at the neck. The upper surface 

 is covered with short but dense hair pointing backwards, and 

 apparently set in quincunx ; the posterior extremity is some- 

 what three-lobed, the middle lobe furnished with a terminal 

 brush of diverging hairs, the outer lobes each bearing a pencil 

 of much longer hairs proceeding from its exterior side, and 

 approaching or crossing the opposite pencil at the tips (Fig. 

 14). From the front of the head projects the prominent 

 tubular mouth ; on each side of which long hairs fall backward 

 as in D. goniathrix, and these, by their vibration, cause a 

 perfect vortex on each side (see Fig. 13), while there is an 

 accessory current also down along the side, and probably all 

 along the belly. But the most remarkable feature in this 

 species is the presence of a pair of antennas or tentacles ; 

 these are nearly as long as the width of the body, are slightly 

 clubbed, and are placed one on each side of the tubular mouth, 

 whence they spring in a curve forwards and outwards. Near 

 the middle of the head is a little rounded mass, somewhat 

 curdled in appearance, which I take to be a cerebral ganglion. 

 An unusually wide and long oesophagus, ventricose behind and 

 permeated by a tube through its centre, leads from the mouth 



