MESOCENA. 



[ 424 ] 



METZGERTA. 



same as M. scalaris ; all the other forms 

 may be brought under M. depressus. 



BIBL. Hassall, Brit. Fr. Alg. p. 166. 

 pi. 41-45; Kiitzing, Sp. Alg. p. 435, Tab. 

 Phyc. v. (Sphcerocarpus] pi. 5-/; Thwaites, 

 Ann. Nat. Hist. xvii. 262. 



MESOCENA, Ehr. A genus of Diato- 

 maceae, according to Ehrenberg and Kiitzing. 



The bodies referred to this title consist of 

 single siliceous rings, oval or angular frame- 

 works, without a centre, and mostly with 

 external and sometimes internal spines ari- 

 sing from them. They have no resemblance 

 in structure to the frustules of the Diato- 

 maceae; they are fossil (marine), and the 

 organic portion is unknown. 



Several species are distinguished, which it 

 can be of no interest to describe ; the cha- 

 racters are founded upon the form, number 

 of angles and spines. 



Whether they are spicula of Echinoder- 

 mata or not, remains to be decided. Diame- 

 ter from 1-750 to 1-400". 



M. octogona, Ehr., PI. 19. fig. 1. 



BIBL. Ehrenberg, Ber. d. Berl. Akad. 

 1840; Kutzing, Bacill. 139, and Sp. Alg. 

 p. 142. 



MESOGLOIA, Ag. A genus of Chorda- 

 riaceae (Fucoid Algse), with filiform, much- 

 branched fronds, of gelatinous character; 

 the axis of the filaments composed of inter- 

 lacing longitudinal cells, with gelatinous 

 interposed matter; the periphery of radia- 

 ting, dichotomous, coloured filaments. The 

 fructification consists of oosporanges and 

 trichosporanges ; the former are ovate sacs 

 (fig. 462) occurring attached to the ramuli 



Fig. 462. 



Mesogloia vermicularis. 



Peripheral ramuli, with oosporanges and the filaments 



upon which the trichosporanges arise surrounding them. 



Magnified 50 diameters. 



of the periphery ; the trichosporanges are 



produced by ramifications of other ramuli 

 surrounding them (fig. 462). Both kinds 

 produce ciliated zoospores, which germinate. 

 M. vermicularis (figs. 462, 463), an olive- 

 Fig. 463. 



Mesogloia vermicularis. 



Portion of a filament. 



Magnified 10 diameters. 



green or yellowish frond, 6" high, is com- 

 mon on rocks and stones between tide- 

 marks. M. virescens, a smaller species, is 

 not uncommon. 



BIBL. Harvey, Brit. Mar. Alg. p. 47. 

 pi. 10 B, Phyc. Brit. pi. 31 & 83; Thuret, 

 Ann. des Sc. not. 3 ser. xiv. p. 237. pi. 27. 



METAXYA, Presl. A genus of Cyathre- 

 ous Ferns. Exotic. 



METEORIC PAPER. See PAPER, 



METEORIC. 



METOPIDIA, Ehr. A genus of Rotato- 

 ria, of the family Euchlanidota. 



Char. Eyes two, red, frontal ; foot forked ; 

 carapace depressed or prismatic; anterior 

 and upper part of head naked or uncinate ; 

 no hood. =Lepadella with two frontal eyes. 



Lorica closed beneath. The characters are 

 doubtful. In one species, the uncination 

 appears (from Ehrenberg's figures) to arise 

 from the so-called respiratory tube, and 

 in another from the head being taper and 

 curved (M. tripterd). 



M. triptera (PI. 35. fig. 7). Carapace 

 ovate, acutely trilateral, crested on the back. 

 Aquatic; length 1-288 to 1-144". 



Two other species, E., to which Gosse 

 adds two. 



BIBL. Ehrenberg, In/us, p. 477 ; Gosse, 

 Ann. Nat. Hist. 1851. viii. p. 201. 



METZGERIA, Raddi. A genus of Pel- 

 liese (Hepaticaceae), comprehending Junger- 

 manniafurcata, L.&ndJ.pubescens, Schrank, 

 growing on trunks of trees, rocks, &c. in very 

 moist places. The fronds of both are linear- 



