582 DESCRIPTION OF [^Tolygadrica. 



Family ASPIDISCINA. 



This family is distinguished from the preceding by the presence 

 of a loricaj alimentary canal distinct, with two orifices, the dis- 

 charging one only being terminal. The lorica is a firm, very trans- 

 parent, combustible little shield, somewhat resembling the shell which 

 covers the back of a tortoise ; it projects anteriorly a Kttle before the 

 body. Long flexible bristle-like organs attached to the abdomen, 

 enable the animalcule to climb, while the delicate cilia near the 

 mouth, serve as s^vimming and purveying organs. Numerou? 

 stomach-cells have been filled with coloured food by Ehrenberg, who 

 has also seen the discharge of matter posteriorly. In one species of 

 Aspidisca, ova and an oval gland are seen; in both a contractile 

 vesicle. MiiUer observed self-division, but mistook it for copulation. 

 They are not developed in large masses. 



Genus Aspidisca. The shield Animalcules. 



A. lynceus. {Triclioda lynceus, M.) — Lorica nearly circular, trun- 

 cated at the posterior end, and formed into a hook or beak in front. 

 This animalcule generally swims or creeps with its back underwards. 

 The mouth has very delicate cilia; the body five or six bristles 

 (styles) posteriorly, and from five to eight hooks anteriorly, resem- 

 bling, in this respect, Euplotes or StylomjcMa. A contractile vesicle 

 near the mouth, and twenty digestive cells have been seen. When 

 burnt upon platina no traces remain. Found amongst duck- weed 

 and Conferva. Size 1-lOOOth to l-576th. 



A. denticulata. — Lorica nearly circular, ends rounded, left side 

 truncated and denticulated ; the back is arched, the abdomen flat, 

 and its hooked bristles are only visible when climbing. Fig. 321, 

 pi. vii., is an under view; and figs. 322 and 323, side views. Size 

 l-576th. 



