DAPHNIA. 



[ 189 ] 



DAVALLIE.E. 



lenses. Labrum (PI. 15. fig. 35) flattened, and 

 with a large hairy lobule at the end. Man- 

 dibles (PI. 15. fig. 34) consisting of a fleshy- 

 looking body, bent inwards near the end, 

 and terminated by numerous minute teeth. 

 Jaws (PL 15. fig. 36) composed of a strong 

 body terminated by four horny spines, three 

 of which are curved inwards. Legs five 

 pairs, those of the first pair in the female 

 (PI. 15. fig. 29) three-jointed; upon the 

 outer edge of the second joint are three small 

 projections, each with four or five long jointed 

 setae ; terminal joint very small, and with 

 one or two similar setae ; the setae not plu- 

 mose. In the male they are more slender, 

 with a strong claw at the end of the second 

 joint, while the seta arising from the termi- 

 nal joint is very long, nearly the length of 

 the body, and floats outside the shells. 



The second (PI. 15. fig. 30), third (fig. 31) 

 and fourth (fig. 32) pairs of legs are bran- 

 chial and somewhat similar, the joints fur- 

 nished with jointed and mostly plumose setae, 

 and a branchial plate also giving off numerous 

 plumose setae. The fifth pair of feet (fig. 33) 

 are three -jointed, the portion corresponding 

 to the branchial plate rounded and without 

 filaments; above this is a curved, jointed, 

 and plumose spine, the third and fourth 

 joints forming finger-like processes springing 

 from the lower end of the foot, with two or 

 three plumose setae. The branchial feet are 

 constantly in motion during life, and this 

 gives rise to the quivering appearance seen 

 in the Daphnue with the naked eye or a sim- 

 ple lens. 



The ova on their escape from the body 

 become lodged between the back of the ani- 

 mal and the shell, where they remain until 

 completely hatched ; but at certain seasons 

 of the year epiphippial or winter-ova (PI. 15. 

 fig. 37) are produced (ENTOMOSTRACA). 



Seven British species of Daphnia are re- 

 cognized : some of them may be found in 

 almost every collection of water, which they 

 frequently colour. 



D.pulex (PI. 15. fig. 28) (common water- 

 flea). Valves oval, their dorsal margin not 

 serrated ; head large, rounded above and in 

 front ; superior antennae (PL 15. fig. 28 a) 

 very small; filaments of inferior antennae 

 plumose ; posterior portion of abdomen with 

 four projections at its curve, the first pro- 

 longed and bent upwards ; below these are 

 two jointed filaments ; the end portion has 

 two dentate arches, and terminates in two 

 strong hooks. 



Some other species are common, but their 



Fig. 160. 



Dasya Kutzingiana. 

 Magnified 50 diams. 



essential characters have not been briefly 

 expressed. 



BIBL. Baird, Brit. Entom. p. 89. 



DASYA, Ag. A genus of Rhodomelaceae 

 (Florideous Algae), con- 

 sisting of tufted filamen- 

 tous sea-weeds, of a red, 

 brown, or purple colour, 

 growing on rocks near 

 low - water mark. The 

 principal filaments are 

 stoutish, branched, and 

 clothed with branched ra- 

 mules, upon which are 

 borne the stichidia con- 

 taining tetraspores (fig. 

 160), or ceramidia con- 

 taining spores, on di- 

 stinct plants. Four British 

 species are recorded, of 

 which D. coccinea and D. 

 Arbuscula are the com- 

 monest. The wood-cut 

 (from Kiitzing) represents 

 a branched raumle bear- 

 ing a stichidium with two 

 rows of tetraspores, from 

 an Italian species. 



BIBL. Harvey, Brit. 

 Alga, 93. pi. 12 B ; PJiyc. Brit. pi. 40. 224, 

 225 & 253\ 



DASYDYTES, Gosse. A genus of Rota- 

 toria, of the family Ichthydina. 



Char. Eyes absent ; body furnished with 

 bristle-like hairs; tail simple, truncate. 



D. yoniathrice. Hairs long, each hair bent 

 at an abrupt angle; neck constricted; 

 length 1-146"; aquatic. 



D. antenniger. Hair short, downy; a 

 pencil of long hairs at each angle of the 

 posterior extremity of the body ; head with 

 two club-shaped organs resembling antennae; 

 length 1-170". 



BIBL. Gosse, Ann. Nat. Hist. viii. 1851. 

 p. 198. 



DASYGL^EA, Thwaites (in Kiitzing). A 

 genus of Oscillatoriaceae (Confer void Algae), 

 forming a shapeless gelatinous stratum in 

 marshy places. One species is described. 



D.amorpAa,Berk.(Pl. 3. fig.ll). Filaments 

 free at the tips, curled and entangled, sheaths 

 very large, 1-220 to 1-50". 



BIBL. Kutzing, SpeciesAlg. p. 272 ; Tab. 

 Phycol. Cent. i. pi. 72. fig. 2. 



DAVALLIA, Sm. See DAVALLIE.E. 



DAVALLIEJ3. A subtribe of Polypo- 

 daeous Ferns, with indusiate sori, containing 

 one genus : 



