148 BRITISH FEESHWATBR EHIZOPODA. 



1. Amphitrema flavum (Archer) Penard. 

 (Plate LVII, figs. 1-5.) 



Ditrema flavum 

 AncHEE in Qrt. Jrn. Micr. Soi. (n.s.) XVII (1877), pp. 336-337, 



pi. xxi, f. 9 (see also p. 103) ; in Proc. Dubl. Mior. Olub, HI, 3 



(1880), pp. 291-292, pi. ix, f. 9 (see also pp. 131-182). 

 TabInbk in Sitzb. bohm. Ges. Wiss. 1881, pp. 224, 235. 

 Blochmann Mikr. Thierw. Siisswass. (1886), p. 16; ed. 2 (1895), 



p. 20. 

 AvEEiNTZBFP in Trudui S.-Peterb. Obshch. XXX, I (1900), p. 240; 



op. cit. XXXI, I (1901), p. 324; XXXYI, ii (1906), pp. 95, 105, 318. 

 ScHOTJTBDBN in Ann. Biol, lacustre, I (1906), p. 373. 

 Beown in Ann. Scott. Nat. Hist. 1911, p. 229. 

 Amphitrema flavum 

 Pbnaed Panne Rhiz. Leman (1902), pp. 534-537, 8 figs. ; Sarcodines 



in Cat. Invert. Suisse (1905), p. 112. 

 Evans in Proc. R. Phys. Soc. Edinb. XVII (1907), table 1. 

 Heinis in Ai-cli. Hydrobiol. V (1910), p. 111. 

 "Wailbs & Pbnaed in Proc. R. Irish Acad. XXXI, Lxv (1911), pp. 14, 



20, 61, 62. 

 Wailbs in Scott. Natni-. 1912, p. 60 ; in Jrn. Linn. Soc, Zool. XXXII 



(1912), pp. 126, 163 ; in Naturalist, 1913, p. 148. 

 Schmidt in Arch. Protist. XXIX (1913), p. 222. 



Test composed of a thick, chitinous, brown, homo- 

 geneous envelope ; in broad view with nearly parallel 

 sides and rounded ends ; in narrow view elliptic ; end 

 views oval, each with a central small oval aperture ; 

 plasma colourless, granular, not completely filling the 

 test, usually loaded with Zoochlorella-celh living in 

 symbiotic relationship ; nucleus single, placed cen- 

 trally, containing a single large nucleole, or two or three 

 small ones; one to three contractile vesicles usually 

 present, also frequently several vacuoles ; pseudopodia 

 filose, straight, radiating, usually few in number. 



Length 45-77 ju.; breadth 23-46 ju,; thickness 15- 

 25 fJL ; aperture 3"5-6'5 /x in broadest diameter ; nucleus 

 about 12 )u, in diameter ; nucleoles 3-4 /u, in diameter. 

 The breadth varies from two fifths to two thirds of the 

 length ; the thickness is usually about half the breadth. 



Habitat. — Sphagnum. 



Essentially a sphagnum-inhabiting species, Amphi- 

 trema flavum is widely distributed over the British 

 Isles and is frequently found in large numbers, espe- 



