Tracheliiia.] infusorial animalcules, 575 



BuKSAKiA nucleus. — Body small, wliite, ovate, attenuated ante- 

 riorly ; extremities convex. Foimd in Hana tentporan'a and Roescu- 

 lenta. Size 1 -240th. 



B. ranarum. — Body ovate, lenticular, and compressed, sub-acute 

 anteriorly ; the back and belly carinated, and often truncated poste- 

 riorly ; mouth inferior, situated near the frontal apex. Size 1-2 10th 

 to l-72nd. 



B. (?) aurantiaca. — Body ovato-oblong ; anteriorly obtuse ; poste- 

 riorly acute ; it has an ash-coloured spot near the mouth. Found 

 amongst Oscillatoria. Size 1 -280th. 



Genus Spieostomum. Tlie snail Animalcules. — Body very elon- 

 gated, flexible, and ciliated, the frontal region continuous; mouth 

 lateral, spirally shaped, devoid of teeth, but with a tremulous flap. 

 The cilia, which are disposed in rows, serve as organs of locomotion ; 

 those at the oblique frontal ridge are longer, and form, as in Stentor, 

 a spii-al wreath around the mouth ; in S. amhiguum the brow and 

 wreath are remarkably long. Digestive cells, to the number of 

 ninety, have been demonstrated by coloured food, and the discharge 

 of the latter observed. They are hermaphrodite. A band-like thick 

 gland is seen in S. virens, and a bead-like one in other species ; the 

 former likewise possess a large contractile bladder, and green ova 

 granules ; but in S. amhiguum the latter are white. Self-division 

 has not been observed, but Ehrenberg presumes a transverse mode 

 exists. 



S. virens. {Bursaria Spirigera, D.) — Body egg-shaped, depressed, 

 truncated anteriorly, and rounded posteriorly. The back is arched, 

 and the mider side flat. The green ova granules are sometimes 

 absent, (f. 296*.) Size l-120th; ova l-6000th. 



S. amhiguum {Leucoplinjs, Triclwda amhigiia, M.) — Body white, 

 cylindiical, filiform, and pliant, obtuse anteriorly, and truncated 

 posteriorly; the body extends very much beyond the mouth, 

 forming an elongated frontal region or brow. The long vibrating 

 cilia in front often appear like a proboscis, and were mistaken for 

 such by Miiller. The structure of this creature is remarkable, 

 especially the mouth, which is only one-fifth from the tail ; thus 

 the front or brow is very long, and the alimentary canal, first 

 inflected forwards, returns along the body. From the mouth to the 



