256 DESCRIPTION OF {Pohjyastrica. 



Genus LXXXVIII. Trichodina. The urn Animal- 

 cules. — Vorticellina destitute both of tail and pedicle. 

 They are distinguished from the preceding genus by the 

 surface of the body being destitute of cilii ; they possess a 

 vibrating fasciculus or wreath of cilii, situated anteriorly ; 

 the oral opening is simple, and not spiral. They are 

 mostly disc-shaped, or conical. Three species have a 

 wreath of cilii around the anterior part, and on one side of 

 the margin is a simple oral opening. T. pediculus has the 

 posterior end abruptly truncated, like the front, and is 

 surrounded with a wreath of curved setae, which it em- 

 ploys as feet. In T. tentaculata there is a kind of pro- 

 boscis. The polygastric structure can be demonstrated in 

 T. pediculus and grandinella by coloured food ; in the 

 other species it may be observed without artificial aid. 

 In all, the ova are clear and limpid as water. A kidney- 

 shaped gland is seen in T. pediculus. 



390. Trichodina tentaculata. The tentaculated Tricho- 

 dina has a discoid- shaped body, as shewn at fig. 227 

 {plate iv.) ; it is destitute of the wreath of cilii, but it has 

 a fasciculus of vibratile cilii, and a styliform proboscis, as 

 seen in the engraving. Size 1 -280th. 



391. Trichodina pediculus (Cyclidium pediculus, (M.) 

 The parasitical Trichodina has a depressed body, of an urceo- 

 late and discoid shape, as shewn at fig. 228, 229, and 230; 

 a wreath of vibratile cilii anteriorly, and another of short 

 moveable uncinated cilii, or hooked setae, upon the back. 

 Ehrenberg remarks, " I have fed this species many times 

 with indigo, and have seen numerous stomachs filled with 

 the blue matter; it always runs upon the back, where 

 there is a wreath of twenty-four to twenty-eight mobile 



