forticellina.'] infttsohial animalcules. 525 



TRicnoDiJTA rorax. — Body oblong, cylindrical, slightly conical ; 

 anterior part convex, and crowned with cilia ; the back rather atten- 

 uated and smooth. Size 1-5 70th. 



T. grand inella (M.) — Is nearly spherical ; the back sharply attenu- 

 ated; a Avi-eath of cilia surrounds the truncated forepart. This 

 species is liable to be mistaken, by an inexperienced observer, for a 

 free Vorticella ; its true character appears to be in its open wreath 

 of cilia. Size l-loOOth to 1.860th. 



We may here describe, owing to the general correspondence 

 between the Urceolaria oi Dujardin, and the Trichodina, of Ehrenbcrg, 

 two species of TJrceolaria described by the former naturalist after Miiller 



Urceolaria Umacina ( Vorticella limacma,^viQ..) — Sessile, cylindrical, 

 diaphanous, sending out from its ti'uncated orifice two to four cilia 

 (difficult to be seen, says Miiller) ; but we may rather suppose the 

 broader anterior end to have a crown of cilia ; whilst the narrower 

 base, by which the animal is aifixed, is furnished with the cilia des- 

 cribed. Foimd on the tentacula and head of Planorhis contortus and 

 Bulla fontanalis, by Miiller. 



Urceolaria — ( Vorticella hursata, and V. utriculata, Mull.) — Dilated 

 posteriorly, truncate and ciliated in front, of a green colour. Foimd 

 in sea -water, Miiller distinguishes two species; one having a 

 papUla, capable of being extended in the form of a long neck ; the 

 other presenting a ti'uncate front with a projecting papilla, from its 

 centre, giving a notched figure to the animalcule when at rest. 



Genus Ueocentrtjji. — The top Animalcules are free, have a tail -like 

 style, but are destitute of pedicle and cilia, except a wreath ante- 

 riorly ; oral aperture simple. The internal organization, as far as it 

 is known, is similar to that of the preceding genera. Perfect trans- 

 verse self-division has been observed. Ehi-enberg thinks the eyes, 

 supposed to have been seen by MiiUer, were most probably the 

 vestigia of some of the cilia, none of which he appears to have seen. 



TJ. turbo {Cercaria turbo, M.) — Is hyaline, and has an ovate, tri- 

 lateral body, with a style, or setaceous tail, one third of its length. 

 Ehrenberg says, " The little tail is not a separable Vorticella-stalk, 

 but an articulated stjle on the back — perhaps a foot. Found 

 amongst Lemna and Conferva. Fig. 232 is a dorsal view, and 231 

 a side view- Size 1- 430th to l-280th. 



