GENUS AMOEBA— AMOEBA PllOTBUS. ' 31 



Protevs diffljwns. Miillcr : Animalcula Infusoria, 1786, 9, tab. ii, figs. 1-12. — Surrixay : Diet. Sci. Nat. 1826. 



Vibrio Proteus. Gmelin: Lin. Syst. Nat., ed. 13, 1788, 3899. 



Amiba divergens. Bory: Diet. Clas. Hist. Nat. 1822, 261. 



Amiba Swaili. Bory: Enoyo. M^thi., Hist. Nat. Zoophytes, 1824, 46. — Dujardin: Hist. Nat. Zoophytes, 



Infus. 1841, 232. 

 Amiba MUlleri. Bory: Enoyc. Mdth., Hist. Nat. Zoophytes, 1824, 46. 

 Amceba princeps. Ehrenherg: Ahh. Ak. Wis. Berlin, 1831, 28, 79; Infusionsthierchen, 1838, 126, Taf. viii, 



Fig. X. — Perty: Kenntniss kleinst. Lehensformen, 1852, 188. — Auerhach: Zeitsoh. wissens. 



Zool. 1856, 407, Taf. xxii, Kg. 1-10.— Leidy: Pr. Ac. Nat. So. 1874, 14,143. 

 Amiba princeps. Dujardin: Hist. Nat. Zoophytes, Infus. 1841, 232, pi. i, fig. 11. 

 Amoeba ramosa. Fromentel: Etudes Microzoaires, 346, pi. xxviii, fig. 2. 

 Amwba communis. Duncan: Pop. So. Review, 1877, 233. 

 Amooba chaos. Leidy: Pr. Ac. Nat. Sc. 1878, 99. 

 Amooba proleus. Leidy: Pr. Ac. Nat. Sc. 1878, 99. 



Species comparatively large, nearly colorless, or more or less black 

 by transmitted light, pale yellowish by reflected light; spheroidal or ovoidal 

 when at rest; very variable and ever changing in shape when in motion, 

 ordinarily ramose,. palmate, or radiate; comparatively active, creeping, with 

 a disposition to differentiate into an anterior and a posterior region. Pseu- 

 dopods digitate, simple or branching, and blunt, sometimes tapering and 

 pointed. Posterior part of the body in contraction receding in the advan- 

 cing pseudopods, sometimes assuming a mulberry -like appearance. Nucleus 

 usually single, discoid, habitually posterior. Contractile vesicle usually 

 single and large, habitually behind the former. Ectosarc thinly differen- 

 tiated. Endosarc finely and coarsely granular, with many and varied ele- 

 ments, contributing in its flow to the extension of the pseudopods. 



Size, in the globular form to 0.2 mm.; in the ovoidal form to 0.3 by 

 015 mm. ; extended in a dendroid form, occupying a space of 6.5 mm. in length 

 by 0.4 mm. in breadth; in a palmate form 0.5 mm. long by 0.35 mm. broad; 

 in a radiate form from 0.2 mm. to 0.5 by 0.4 mm. ; in an irregularly cyHndroid 

 form to 1 mm. long. The largest observed occupied a space of 0.6 by 0.2 

 and 0.35 mm. 



Locality. — Common in the superficial ooze of ponds and ditches almost 

 everywhere, though rarely in large numbers. Ditches below Philadelphia 

 and brick-ponds in the vicinity. Ponds in the neighboring counties, 

 including Delaware, Che^ster, Montgomery, Bucks, Berks, and Northamp- 

 ton; Broad Mountain, Schuylkill County; Pokono Mountain, Monroe 

 County, Pennsylvania; at Absecom, Hammonton, Woodstown, Vineland, 

 Cape May, and other places in New Jersey; Newport and Narragansett, 

 Rhode Island ; and lakes of the Uinta Mountains, Wyoming Territory. 



A large Ai»«Bba is the subject of the earliest notice of a Fresh-watei 



