ACTINOCYCLUS. 



[ 12 ] 



ACTINOPHRYS. 



of exotic Algae (marine!, referred to Rivu- 

 laria by Suhr (Kiitz. Tah. Phyc. 31. fig. 2). 



ACTINOCYCLUS.— A genus of Diato- 

 macese. 



Char. Frustules solitary, free or adherent 

 to other bodies; disk-shaped; valves circu- 

 lar, exhibiting apparently cellular markings, 

 with rays or bands radiating from the centre, 

 Avhich is free from the cellular appearance ; 

 no internal septa ; marine. 



The cellular appearance arises from the 

 existence of depressions upon the surface. 

 The radiant bands arise from undulations of 

 the surface, which are best seen in the front 

 view (PL 18. fig. 43 b). 



Only 1 British species, A. undulatus 

 (PI. 18. fig. 43 a); rays 6, diam. 1-250 to 

 1-1100". 



Kiitzing enumerates 34 species ; some are 

 found fossil. 



BiBL. Ehrenberg, Leb. Kreidethierchen, 

 1840, p. 57 ; Monatsbericht, 1844 ; Kiitzing, 

 Kieselschaligen Bacillar. 1844; Species Al- 

 garum, 1849. 



ACTINOGONIUM, Ehr.-A genus of 

 Diatomaceae. 



Char. Prismatic, frustules not forming a 

 filament, sub-spherical, with /or more angles. 



A. septenarium. With 7 angles. Found 

 fossil in Barbadoes earth, with Polycystina. 



Not British. 



BiBL. Ehv. Monatsber.d.Berl.Akad.\847; 

 Ann. Nat. Hist. vol. xx. p. 127. 



ACTINOPHRYINA, Duj.— A family of 

 Infusoria. 



Char. Animals without appreciable or- 

 ganization; immoveable or fixed; provided 

 with variable, very slowly contractile, always 

 simple expansions, the ends of which by con- 

 traction frequently become globular. 



This family corresponds with Ehrenberg's 

 Acinetina, and includes 5 genera : Podo- 

 phrya, Actinophrys, Acineta, Trichodiscus 

 and Dendrosoma. 



ACTINOPHRYS.— A genus of Infusoria, 

 of the family Acinetina, E. ( Actinophryina, D.) 



Char. Body without vibratile cilia, having 

 numerous setaceous tentacles radiating on all 

 sides (mouth abruptly truncated), E. 



Dujardin says, body s])herical or discoid- 

 al, surrounded with radiating, filiform, very 

 delicate and slowly contractile expansions. 

 Species : — 



A. sol, E. and D. (PI. 23. fig. 7b). Sphe- 

 rical, whitish tentacles radiating from all 

 parts of the body, once or twice as long as 

 its diameter, D. (rather less than once, E.); 

 diam. 1-430 to 1-1200"; aquatic. 



/3 (?) A. Eichornii, E. Diam. MOO" (PL 23. 

 fig. 7 a). ^ 



y marina, D. Colourless, contractility of 

 tentacles greater, marine. 



A. digitata,J}. Colourless, body depressed, 

 rays flexible, thickened at the base, and when 

 contracted forming finger-like prolongations; 

 diam. 1-770; aquatic. 



A. discus, D. {Trichodiscus sol, E.), PL 

 25. fig. 8. Hyaline or yellowish ; body dis- 

 coidal, depressed, a ring of radiating taper 

 tentacles arising from one portion of the 

 body only; diam. 1-210 to 1-430"; aquatic. 



A. difformis, E. and D. Colourless ; body 

 irregularly lobed ; rays variable, taper ; 

 diam. 1-280 to 1-570"; aquatic. 



A. pedicellata, D. (Podophrya jixa, E.), 

 PL 23. fig. 5 a. Body spherical, whitish, 

 exhibiting a cellular appearance, from the 

 presence of numerous vacuoles (?), furnished 

 wdth a peduncle ; tentacles capitate, as long 

 as the body is broad ; diam. 1-430"; aquatic. 



/3 salsa, E. Tentacles not capitate ; ma- 

 rine. 



A. viridis, E. and D. (PL 23. fig. 6). Body 

 spherical, greenish; rays numerous, taper, 

 shorter than the body ; diam. 1-280 to 

 1-620" ; aquatic. 



A. granata, D. Spherical, opake in the 

 centre ; rays taper, shorter than the body. 



Diff^erent opinions are held as to the man- 

 ner in which these animals are nourished. 

 M. Stein says that no foreign particles ever 

 enter the body. M. Ehrenberg admits the 

 existence of a mouth and an anus at opposite 

 ends of the body. Mr. Brightwell says that an 

 infusorium, when entangled by the tentacles 

 (expansions), is absorbed into the body of 

 the animal by its surface, or by the thicker 

 expansions of the body. The most recent 

 writer upon Actinophrys {sol) ?, M. Kolliker, 

 considers the body to be composed of a ho- 

 mogeneous substance wdth granules and va- 

 cuoles, some of the latter, which give it a 

 cellular appearance near the centre, contain- 

 ing nucleated cells. He states that an in- 

 fusorium, or a minute alga, coming into 

 contact with one of the tentacles, generally 

 becomes adherent. The tentacle with the 

 prey then slowly shortens, and the surround- 

 ing tentacles apply themselves upon it, bend- 

 ing their points around the captive, so that 

 it gradually becomes enclosed on all sides. In 

 this way the prey is gradually brought to the 

 surface of the body. The spot at the surface 

 of the bodyuponwhich the captured organism 

 is lying slowly retracts, and forms at first a 

 shallow depression, which gradually becomes 



