L1THAMCEBA DISCUS. 83 



The nucleus is large, peculiar in shape (''block-like "), 

 distinctly punctated or tesselated, and has a definite 

 capsule. In the structure of this organ, and the delicate 

 cuticle of its protoplasm, Litliamwba is considered by 

 its author as " unlike any other form, whilst the com- 

 bination of characters which it presents entitles it to a 

 very distinct position among the amoeboid Gymno- 

 myxa." 



The organism is apparently very rare. We have 

 not met with it. The foregoing description is taken 

 from Prof. Lankester's monograph. 



Genus 6. OURAMCEBA Leidy, 1879. 



Amoeba, (pars) ARCHER in Q. J. Micr. Sci. VI, n.s. (1866), 



p. 190. 

 Ouramueba LEIDY Freshw. Rhiz. N. Amer. (1879), p. 66. 



Body amoeboid, with a granular endoplasm, a single 

 contractile vesicle, and discoid nucleus. Pseudopodia 

 digitate, arising from any part of the body-surface, 

 usually anterior; the posterior extremity habitually 

 furnished with one or more tufts of rigid, linear, non- 

 contractile protoplasmic filaments, branching radially 

 from points in the vicinity of the contractile vesicle. 



The posterior filaments, which are the peculiarity of 

 this genus, alone distinguish it from Amceba. These 

 filaments are sometimes cast off, and by some authors 

 have been held to be of no physiological significance. 



1. Ouramceba vorax Leidy. 

 (Plate V, fig. 6.) 



villosa (Wallich) ARCHER in Q. J. Micr. Sci. VI, 

 n.s. (1866), p. 190; op. cit. X, n.s. (1870), p. 305; in 

 Journ. Dublin Micr. Club, I, 2 (1867), p. 56; and op. cit. 

 II, 1 (1872), p. 15. 



villosa ? ARCHER in Q. J. Micr. Sci. XIV, n.s. (1874), 

 p. 212, and in Journ. Dublin Micr. Club, II, 3 (1875), 

 p. 314. 



