ACHROMATISM. 



[ 11 



ACHRO'MATISM. — A term properly 

 sig-nifyiujr freeclt)iu I'roiu cliromatie aber- 

 ralion, but commonly used to denote free- 

 dom from both spherical aud chromatic 

 aberration. 



A CIC LTL A'RIA, D' Archiac— One of the 

 Foraminifera imperforata, related to Dac- 

 tyhpuru, aud consisting- of numerous cham- 

 bers arranged in close order side by side 

 without intercommunication, and forming 

 minute aciculate cylinders, or narrow ta- 

 pering plates. Known fossil only in some 

 Tertiary beds of France. 



BiBL. Carpenter, Introcl. For am. 137. 



ACIXE' RIA, Duj . — A genus of Infusoria, 

 of the family Trichodiiiia. 



Char, Body oblong or lanceolate, de- 

 pressed, the i'ore part somewhat obUquely 

 recurved like the blade of a sabre ; a row of 

 cilia,directed foiwavds, arisingfrom one side. 



Dillers from Traclidius, Buj., in the ar- 

 rangement of the cilia aud in the anterior 

 curvature; devoid of a mouth, like Trache- 

 lius, Avhich especially distinguishes the pre- 

 sent genus from Pclecida. "2 species : 



A^ incurvata (PI. 30. fig. 1) ; marine, 

 colourless ; length 1-590 inch. 



A. acuta (PL 30. fig. 2), found in fresh 

 water ; length 1-580 inch. 



Bujardiu figures in the latter species cilia 

 upon both margins, those on one side being 

 directed forwards, and those on the other 

 backwards. 



Claparede and Lachmann refer these to 

 Amphileptus, 



BiBL. Dujardin, /ji/«s. p. 402; Clap, and 

 Lachm. Inf. p. 356. 



ACINETA, Ehr.— A genus of Rhizo- 

 poda, belonging to the family Aciuetina. 



Claparede aud Lachmann enumerate 8 

 species. 



A. iwjstacina (PL 51. fig. 11). Yellowi-h 

 brown, rounded, tentacles in two bundles ; 

 1-120 to 1-800. On Lcmna minor. 



A. patida (PL 51. fig. 12). Body as if 

 resting on a cup-shaped carapace, variable 

 in form; contains brown granules. On 

 marine AlgiB. Norwav. Length 1-100". 



A. iuherosa (PL 30. 'fig. 4). Colourless 

 or yellowish brown, triangular wlien ex- 

 panded; tentacles arising from the distal 

 angles only. Salt or brackioh waters; 1-lCO" 

 to 1-410". 



A. Lyncjhyi, fcrrum-equinum, and cylin- 

 drica are referied by Ci. aud Lachm. to 

 Podophrija. 



A. Notoncdee. On the hairs of the legs of 

 N. glauca. 



] ACINETINA. 



BiBL. Vmcmi,Ann. d. Sc. Nat. 3 s^r. Zool. 

 iii. & ix. ; Ehr. Inf.; Duj. Inf.; Claparede 

 and Laelimann, I^tiidex, ^-c. ; Ann. N. II. 

 1857, xix. ; Stein, Infm.; Cegenbaur, 

 3Iorph. Jaln-h. 1875. 



ACINETI'NA, Ehr.— A family of Radio- 

 larian Rliizopoda. 



Char. Those of the Actinopliryina, but 

 with usually capitate aud suctorial tubular 

 tentacles, the body being more or less en- 

 closed in a carapace, which is generally 

 prolonged to form a stalk. 



The structure and relations of these ani- 

 mals are still very unsettled. The re- 

 searches of Pineau and Stein tended to 

 render the existence of the species doubtful, 

 by showing that they were stages of deve- 

 lopment of Episti/lis, Va(/inicola, Vorticella, 

 &c. ; but this has since been found to be in- 

 correct. They exliibit a nucleus, and one 

 or more contractile vesicles. The remark- 

 able suctorial character of the tentacles has 

 not been proved to occur in all the genera 

 and species. Many, however, have been 

 seen to take food voraciously, which is thus 

 effected : when an Infusorium touches the 

 button-like end of the tentacle, it usually 

 remains adherent to it ; the end becomes still 

 more dilated so as to constitute a sucking 

 disk, and the ray becomes thicker and 

 shorter, the other rays at the same time 

 making grasping movements and endea- 

 vouring to attach their extremities to the 

 captured prey. A current of chyme-par- 

 ticles is then soon seen running from the 

 captured infusorium into the body of the 

 Acineta. The chyme-particles form at first 

 a slender row,but afterwards collect in a drop. 

 The body of the Acineta then becomes 

 opaque, from the collection of the drops. 



The colourless or coloured ova described 

 by Ehreuberg ai'e partly chyme-particles, 

 partly oil drop-like globules which make 

 their appearance in the Acindcs after ani- 

 mal food. The ciliated swarm-germs to 

 which they give origin have been traced 

 directly into .Acinetce. Fission has been 

 observed in Acineta vii/stacina, not in the 

 others. The genera may be thus divided : 



*Tt'ntaele9 not borne upon a proboscis. 

 Tentacles unbranched. 

 Stalks simple. 



fA peduncle 1. Podophriia. 



Ko shell < Xo pedun- (free.. 2. Sphrrophrya. 

 \_ cle ) fixed. 3. Trichophrj/a.] 



A sh >n (Pfli'ic'p present. 4. Acineta. 



'"' ") Peduncle absent... 5. Solenophri/a. 



Ftalka branched 6. Dendrosoma. 



Tentacles branched 7. Dendromycetes. 



**Tentacles borne on a long pro- 

 boscis 8. Ophryodendrion. 



