DISTEMMA. 



[ 214 ] 



DOLICHOSPERMUM. 



DISTEMMA, Ehr. A genus of Rotatoria, 

 of the family Hydatinsea. 



Char. Eyes two, cervical ; foot forked. 

 D.forficula (PI. 34. fig. 25; fig. 26, teeth). 

 Body cylindrico - conical ; eyes red; toes 

 strong, recurved, toothed at the base ; aqua- 

 tic; length 1-120". 



Three other species, two of which are 

 aquatic, and one marine. In the latter, D. 

 marina, the cervical eye-spots are colourless; 

 if these do not really represent eyes, this 

 species must be referred to the genus Pleuro- 

 trocha. 



BIBL. Ehr. Infus. p. 449. 

 DISTICHIACEjE. A family of opercu- 

 late Acrocarpous (terminal-fruited) Mosses, 

 of csespitose habit ; the stem increasing to- 

 wards the point, simple or branched; the 

 leaves with a dorsal keel-like nerve, equitant- 

 concave, densely imbricatively overlapping, 

 parenchymatously areolated. Cells minute, 

 with thick walls, somewhat papillose, very 

 densely packed, squarish. Capsules oval, 

 equal. British genus : 



DISTICHIUM, Br.and Schimper. Calyp- 

 tra dimidiate. Capsule annulate. Peristome 

 simple, with sixteen equidistant teeth, free 

 at the base, once or several times slit from 

 the base to the apex, trabeculate, deep pur- 

 ple, homogeneous, smooth or rough. Inflo- 

 rescence monoecious. British species : 



Distichium capillaceum, Br. and Sch. = 

 Didymodon capillaceus, Schrad. 



D. inclinatum, Br. and Sch.=Didymodon 

 inclanatus, Sw. 



DISTIGMA, Ehr. A genus of Infusoria, 

 of the family Astasiaea. 



Char. Unattached, eye-spots two, blackish. 



There are no cilia, flagelliform filaments, 



nor other locomotive appendages; motion 



similar to that of a leech. Body variable in 



form. 



D. proteus (PI. 23. fig. 46 a). Body hya- 

 line, obtuse at the ends, alternately contracted 

 or expanded from side to side; eye-spots 

 distinct; aquatic; length 1-570 to 1-430". 



D. viride (PI. 23. fig. 46 b}. Body filled 

 with green granules, alternately contracted 

 and expanded ; eye-spots distinct ; aquatic ; 

 length 1-570". 



Two other aquatic species; one yellow, 

 the other colourless. 



BIBL. Ehr. Infos, p. 116. 

 DISTOMA, Zeder. A genus of Entozoa, 

 of the order Sterelmintha, and family Tre- 

 matoda. 



Char. Body soft, depressed or cylindrical, 

 more or less elongated, not jointed; fur- 



nished with two distinct and isolated suckers; 

 one anterior, terminal, and containing the 

 mouth, the other situated on the ventral 

 surface between the middle and the anterior 

 sixth of the body. 



The species are very numerous ; Dujardin 

 describes 164. They are most common in 

 birds and fishes, generally inhabiting the 

 alimentary canal. 



D. hepaticum, the fluke. Occurs in the 

 gall-bladder and hepatic ducts of sheep when 

 aifected with the 'rot.' It has also been 

 found in the horse, the ox, the goat, the 

 hare, and the stag. Length 4-5 to 1^". 



Some of the other species are micro- 

 scopic. 



BIBL. Dujardin, Hist. nat. d. Helminth. 

 p. 381 ; Mehlis, Obs. de Distom. hepat. fyc. 

 1825 ; Beneden, Ann. des Sc. nat. 3 ser. 

 Zool. xvii. 



DOCIDIUM^relnsson. A genus of Des- 

 midiacese. 



Char. Cells single, straight, much elon- 

 gated, linear, sometimes attenuated towards 

 the ends; constricted at the middle, ends 

 truncate; segments usually inflated at the 

 base. 



Docidium, like Closterium, has the termi- 

 nal spaces with moving molecules ; and its 

 vesicles are either scattered or arranged in a 

 single longitudinal row. 



D. truncatum (PI. 10. fig. 38). Segments 

 three or four times as long as broad, with a 

 single inflation at the base ; suture project- 

 ing on each side ; length 1-80 to 1-72". 



D. baculum (PI. 10. fig. 39). Segments 

 very slender, with a single conspicuous infla- 

 tion at the base, otherwise linear ; vesicles in 

 a single series; length 1-111". 



D. nodulosum. Segments four to six times 

 as long as broad, constricted at regular in- 

 tervals so as to produce an undulated margin ; 

 suture projecting; length 1-50". 



Three or four other species. 



BIBL. Ralfs, Brit. Desmid. p. 155. 



DOLICHOSPERMUM, Thwaites (PI. 4, 

 fig. 2). A genus of Nostochacese, allied to 

 Trichormus, Sphcerozyga, &c., established 

 by Thwaites for five British species, from 

 which Hassall has separated one under the 

 name of Coniophytum. Thwaites noticed in 

 this genus that the contents escaped in an 

 undivided mass from the elongated and 

 mostly cylindrical spermatic cells, which are 

 invariably truncated at the ends. 



1. D. inaquale, Ralfs. Filaments monili- 

 form ; ordinary cells at first quadrate, finally 

 orbicular ; vesicular cells large, spherical ; 



