NAUPLIUS. 



[ 534 ] 



NECTRIA. 



It is questionable how far this genus is 

 different from Chilodon. 



BIBL. Ehr. In/us. 338; Stein, Inf. 248; 

 Cohn, Qu. M. Jn. 1859 ; Clap, et Lachrn. 

 Etudes ; Kent, Inf. 494. 



NAUTLIUS. See CRUSTACEA, p. 216. 



NAVICELL^E. See GHEGAMNA, p.36o. 



NAVIC'ULA, Bory. A genus of Diato- 

 maceae. 



Char. Frustules single, free; valves ob- 

 long, lanceolate or elliptical, sometimes with 

 the ends narrowed and produced, rarely 

 constricted in the middle, furnished with a 

 longitudinal line or keel, and a nodule in 

 the middle and at each end; surface of 

 valves covered with dots arranged in trans- 

 verse or slightly radiating rows, producing 

 an appearance of lines, although both dots 

 and lines are often invisible by ordinary 

 illumination. 



Valves usually symmetrical, and the keel 

 median ; but in two species the keel is 

 sigmoid and the valves inequilateral. Some- 

 times the keel is double. There is mostly 

 a little space between the rows of dots 

 (PI. 15. fig. 8), so that these readily exhibit 

 transverse lines or striae by unilateral oblique 

 light; but sometimes they are pretty uni- 

 formly distributed, as in many of the species 

 belonging to the first section of Pleuro- 

 siffma. 



Species or forms very numerous ; Kiitzing 

 describes 170, some of them, however, be- 

 longing to Pinnularia, Pleurosigma, and 

 other genera. Rabenhorst notices 237 spe- 

 cies. Many may have been derived from 

 a frustule of a Schizonema or Colktonema 

 which had escaped from its gelatinous 

 envelope I 



The formation of sporangial frustules has 

 been noticed by us in Navicula amphirhyn- 

 chus, and they are contained in a siliceous 

 sporangial sheath or case. The process is 

 sufficiently illustrated by the figures (PI. 50. 

 figs. 19-24) : fig. 19, side view of the parent 

 frustule ; fig. 20, front view of conjugating 

 frustules, with young sporangial sheath; 

 fig. 21, empty mature sheath ; fig. 22, 

 crushed empty sheath and parent frustules 

 in situ ; fig. 23, sheath, one parent frustule 

 and sporangial frustule in front view ; fig. 

 24, sporangial frustule in side view. 



N. cuspidata (PL 15. fig. 6, side view; 

 fig. 7, front view ; , hoop). Valves lan- 

 ceolate, somewhat rhomboid, acuminate; 

 freshwater; length 1-350 to 1-200". ^ Valves 

 slightly iridescent, no striae by ord. ilium. 



N. didyma (PI. 15. fig. 9). Valves ellip- 



tic oblong, slightly constricted in the middle; 

 marine; length 1-000 to 1-300". Ends 

 sometimes broadly rounded, and the con- 

 striction very deep. 



N. rhomboides. Valves rhomboid-lanceo- 

 late; colourless and not striated by ordin. 

 ilium.; freshwater; length 1-350". Striae 

 85 in 1-1000" (8m.). 



N. amphirhynchm (PI. 50. fig. 19, side view ; 

 fig. 22, front view of conjugating frustules). 

 Valves linear, or nearly so, suddenly con- 

 tracted near the produced and obtuse ends j 

 freshwater ; length 1-500 to 1-250". 



N. affinis. Valves elliptical, contracted 

 and linear towards the rounded ends; fresh- 

 water. 



BIBL. Smith, Br. Diat. i. 46 ; Kiitz, Ba- 

 cill. 91, and Sp. Alg. 69 ; Grev., n. sp., Mic. 

 Tr. 1866, 84 & 126; O'Meara, pec. forms, 

 Qu. Mic. Jn. 1872, xii. 283 ; Rabenh. Ala. i. 

 169. 



NEBA'LIA, Leach. A genus of Phyllo- 

 podous Entomostraca. 



Char. Antennae two pairs, large and rami- 

 f orm ; eyes two, stalked ; legs twelve pairs, 

 eight branchial and four natatory ; carapace 

 large, enclosing head, thorax, and part of 

 abdomen. 



N. bipes (PI. 19. fig. 28). Marine; body 

 yellowish ; length 3-8". 



BIBL. Baird, Br. Entom. 36 ; Glaus, Sieb. 

 Sf Koll. Zeits. 1872,- 323 ; An. N. H. 1879, 

 iv. 418. 



NECKE'RA, Hedwig. A genus of Hyp- 

 noid Mosses. 



Elegant little perennial plants, growing 

 on trunks of trees and shady rocks, having 

 stems pinnately branched, bearing compla- 

 nate leaves arranged in eight rows (fig. 484). 



N. crispa, Dill., found in mountainous 

 districts, is a large moss, with stems 4 or 6" 

 long or more, growing horizontally from a 

 creeping rhizome. 



NECTRIA, Fries. A genus of Sphaa- 

 riacei (Ascomycetous Fungi), distinguished 

 from true Sphcsrice by the free, membranous, 

 flaccid, brightly coloured perithecium, the 

 pale papilla, and the gelatinous pale nucleus 

 expelled in the form of a drop or of white 

 flocks ; the asci contain eight pellucid 

 spores. The imperfect forms of these plants 

 are described as distinct genera. Thus 

 Tubercularia vulgaris, common on bark of 

 dying or dead trunks, and on dead twigs of 

 birch especially, ripens into N. cinnabarina ; 

 this we have observed ; and it is probable 

 that other Coniomycetous forms will require 

 to be reduced in like manner. Nectria 



