88 



I. IJIMA. 



tually spherical or more frequently ellipsoidal, characterized by having at one 

 pole a small rounded protuberance, which on close observation is found to bear 

 on its surface a number of fine processes, the pseudopodia, closely set and extend- 

 ed to a greater or less degree. The protuberance is apparently the same struc- 

 ture as the " villous knob " or " Zottcnanhang " which has long been known to 

 characterize the hind end of certain species of Amœbœa (Amœba vd'osa Wallich, 

 Am. fluida Gruber, Pelomyxa lilloaa Leidy).* 



The size of the body is variable within certain limi's. Large specimens 

 have a diameter of 38 fi, while the smallest may measure not more than 15 ft 

 across. They never attain the size of Am. fluida (80 — 90 ß, according to 

 Greeff), which, of all the Amoeba species known to me seems to come nearest 

 to the present one in several respects. 



The sarcode is, apart from its enclosures, clear and uniformly finely granu- 

 lar, without perceptible differentiation into the ectoplasm and the endoplasm 

 except at the villous knob. The substance of the latter is clearer and hyaline, 

 without enclosures of any kind. I think I may say that it represents the main, 

 if not the entire, mass of the ectoplasm of the present species, localized as it were 

 at the spot in questien. This view also coincides with the fact that the general 

 surface never involves itself in any considerable movements. 



The villous knob may be papilliform or hemispherical in shape, measuring 

 about 10 fx across at the base. At other times it is only a gentle elevation and 

 under certain circumstances, may even be entirely retracted or obliterated. On 

 small specimens, such as represented in fig. 5 a — d, I have frequently missed the 

 knob. It is possible that in some of such cases it was simply concealed from view, 

 being situated at a position turned away from or towards the sight ; in certain 

 other cases however I was convinced of its absence. In these latter cases, short 



* Am. villos-i is a fresh-water species first discover?.! and described by Wallich in En- 

 gland (Ann. & Mfg. Nat. Hist. 18<>3). Whether the forms reported under the same ntnie by 

 I EiDY ( Fresh-water Rhizopoits of N. America, 18 '9) and by Monies (lihiz^podenfauna der 

 Kieler Bucht ; Abb. d. k. pr. Akad. d. Wiss. zu Berlir, lf"88) were correctly identified, seems 

 to require corroboration. — Am. fluida is a marine species first de cribed by Gkubkr (Z. f. w. 

 Z. t'D. 41, p. 219) and later more preci ely by Grv.ekf (Biol. Centralbl. B I. 12, p. 374). This is 

 a species that seems most to resemble Am. miurai. — Pelomyxa u/7/o-a was de .cribed by Leidy in 

 bis '' Fre-h-W;iter Rhizopods of N. Amerio .)," p 75. — All the^e specie* luve in common with 

 An. miitrai the characteristic villous knob, though it can not be said that this structure is 

 strictly confini d to the species mentioned. As to the specific distinction between Am miurui 

 and the three specie- above cited let it suffice to mention here that the latter are all much 

 larger in size, are capable of active, typically amoeboid or flowing motion with the main body 

 and inclose in the endosarc crystals, pigments or peculiar bodies such as are not obs rved in 

 Am. miurai. 



