DTSTIGMA. 



[ 268 ] 



DOCIDimi. 



DISTIG'MA, Ehr.— A genus of Infuso- 

 ria, of the family Astasisea. 



Char. Unattached, two blackish eye- 

 sp(its, 



Flagelliform filaments two, one long, one 

 short ; motion similar to that of a leech. 

 Body variable in form ; freshwater. 



B. protem (PL .30. fig. 4(3 a). Body 

 hyaline, obtuse at the ends, alternately 

 contracted or expanded from side to side ; 

 eye-spots distinct ; length 1-570 to 1-430". 



B. viride (PI. 30. fig. 46 b). Body filled 

 with green granules, alternately contracted 

 and expanded ; eye-spots distinct ; length 

 1-570". 



Two other species ; one yellow, the other 

 colourless. 



BiBL. Ehr. Bifus. 116; Kent, L>f. 418. 



DIS'TOMA, &a3rtn.— A genus of Mol- 

 lusca, of the order Tunicata, and family 

 Botiyllidaj. 



Distinguished by the sessile, semicarti- 

 laginous, polymorphous mass ; the numerous 

 circidar systems ; the individuals in one or 

 two rows at imequal distances from a com- 

 mon centre, with thorax and stalked abdo- 

 men ; and the branchial and anal orifices 

 six-rayed. On marine Algie {Fuciis ^•c). 



B. rubrum (PL 30. fig. 23). Mass red, 

 individuals yellowish; 5" in diameter, 5" 

 thick. 



B. variohsinn. Reddish- or yellowish- 

 white ; bodies orange-red. 



BiBL. Forbes and Hanlev, Br. Moll. i. 

 18. 



DIS'TOMA, Zeder, or Bisfomum.—A 

 genus of Entozoa, of the order Sterehnintha, 

 and family Trematoda. 



C/iar. iiody soft, depressed or cylindrical, 

 more or less elongated, not jointed, brown ; 

 furnished with two distinct suckers — one 

 anterior, terminal, and containing the 

 mouth, the other situated on the ventral 

 surface between the former and the middle 

 of the body. 



Species very numerous ; Dujardin de- 

 scribes 164 ; most common in birds and 

 fishes, generally inhabiting the alimentary 

 canal. Each Bistoma has its separate Cer- 

 caria, which live in as many distinct 

 animals. 



B. hepaticum (the fluke) occurs in the 

 gall-bladder and hepatic ducts of slieep 

 when affected with the ' rot ' ; it occurs also 

 in the horse, the ox, the goat, the hare, the 

 stag, and in man. The intestine is two- 

 branched, and the branches ramified. 

 Length 4-5 to 1}". 



B. hepaticum is of special interest, on ac- 

 count of the immense destruction it causes 

 of sheep. When the young Bistoma leaves 

 the ovum, it resembles an obconical cilia- 

 ted Infusorium, with a short terminal pro- 

 boscis ; the cilia are subsequently cast off, 

 and a sporocyst or Beclia is formed, which 

 attaches itself to MoUusca, and in which 

 numerous CercaricB are then produced. 

 These when liberated, swim in water, and 

 are swallowed by sheep, or the moUusca 

 containing them are eaten with the grass ; 

 and so the young Bistomata enter the ali- 

 mentary canal, to take up their final abode 

 in the biliary ducts. 



B. lanceolatmn has the intestine once 

 branched, then simple ; it occurs in the 

 liver of man, the ox, the sheep, the pig kc. 



B. (Bil/iarzia) hcematohia, the African 

 Trematode, has the body vei-miform ; the 

 male I", the female 1" long. It is found 

 in the bloodvessels of man in Egypt, Mau- 

 ritius, South Africa, &c. 



B. sinensis occurs in the liA'cr of the 

 Chinese. 



Some of the species are microscopic. 



BiBL. Dujardin, Helminth. 381 ; Bene- 

 den, Ann. Sc. Xat. 3 ser. Zool. xvii. ; Cob- 

 bold, Parasites, 1879, xiv. ; BoAvles, Sheep- 

 rot ; Tirties {remedy) Apr. 10, 1881 ; Ann. 

 N. H. 1880, vi. 40o; Sommer, Aymt. 1880. 



DITTO LA.— A genus of Tremellini 

 (Basidiomycetous Fungi) consisting of 

 saucer-shaped -margined gelatinous Fungi, 

 wdth a discoid hymenium, which is at first 

 veiled. Bitiola radicata occurs rarely in 

 this country on decayed firwood. B. tiiida, 

 B. and Br., is considered by Tulasne syno- 

 UATnous with Bacrymi/ces deliquescens. 

 " BiBL. Alb. & Schwein. pi. 8. f . 6 ; Berk. 

 Oidl. p. 291. 



DOCH'MIUS, Duj.— A genus of Xema- 

 toid Entozoa. 



B. {Anchi/losfoma) ditodenalis is filiform, 

 the head pointed and curved ; the mouth 

 with four unequal converging curved teeth ; 

 body pointed behind in the female, blunt in 

 the male ; viviparous; length of male -f", 

 of female ^". Occurs in the human small 

 intestines, in Italy, Austria, Egypt, and 

 South America, producing anaemia and 

 chlorosis. 



B. trigonocephalus, in the dog. 



B. Sangeri, in the elephant. 



BiBL. Dujardin, Helm. 

 Paras. 211 (fig.). 



DOCIDTUM, Brebisson.— A 

 Desmidiacese. 



/O 



; Cobbold, 



genus of 



