ZOOTEIRA. 



[ 827 ] 



ZYGNE]\rA. 



Spermatozoids are transitory structures ; 

 when discharged from the parent cell, they 

 oither make their Avav to a germ-cell of a 

 spore, fertilize it and disappear, or, if de- 

 barred from this, at once perish without 

 germination. As stated under SpEn:\rATO- 

 zoiDS, these bodies vary much in form. In 

 the higher Cryptogamia they are spiral fila- 

 ments (PL 40. tigs. 31-4). In the Fucaceae 

 they are minute globular bodies with two 

 cilia (fore and aft) closely resembling some 

 zoospores ; in the Florideae they are globules 

 without cilia : and those recently described 

 as existing in VArcHEEiA, amoiig the Cou- 

 fervoids, are also biciliated globules with 

 the cilia fore and aft, while those in Sph^- 

 ROPLEiE resemble the microyonklin of this 

 family, having their pair of cilia on the beak ; 

 in CEcoGOxirM they resemble the zoospores, 

 but are smaller. The latter observation is 

 in favour of the microgonidia of Hydrodic- 

 tifon, &c. being spermatozoids. 

  ZOOTEI'RA, Wright.— A genus of Ac- 

 tinoplu-yina (Rhizopoda). 



Char. Body furnished with numerous 

 contractile acuminate rays, elevated on a 

 contractile pedicel ; the rays become thick- 

 ened towards the point when not fully ex- 

 panded. 



BiBL. Wright, Prifchard's Infusoria, 

 563. 



ZOOTHA^l'NIUM, Ehr.— A genus of 

 Vorticellina (Peritrichous Infusoria). 



Char. Body like Vorticella, usually of 

 different shapes, attached to the ends of 

 a branched zoary ; internal muscle branched 

 and continuous. Many s " 

 fresh water. 



Z. arhuscula (PI. 32. fig. 22). Branches 

 of polypidconi racemose-umbellate, bodies 

 white, stalks very thick. Freshwater j 

 length of polvpidom 1-4" ; of bodies 1-430' '. 



BiBL. Ehr. Infm. 288 : Stein, Inf. ; Clap. 

 & Lach. Inf. 101 ; Kent, Inf. 693." 



ZOS'ENIE, Boeck. — A genus of Copepoda. 

 Z. typica, in dredgings. (Brady, Copepoda, 

 ii. 14.) 



ZOS'TERA, L. -Agenusof Monocotyle- 

 donous Flowering plants (Nat. Ord. Zostera- 

 ceas), gi-owing in sea- water ; remarkable for 

 the Pollen, of which the grains are repre- 

 sented by tubular filaments destitute of an 

 outer coat and exhibiting Rotation when 

 fresh. 



ZYGNE'MA, Agardh, in part {Tynda- 

 ridea, Bory, Hassall). — A genus of Zygne- 

 macese (Confervoid Algae), consisting of 

 filamentous plants, with the gi'een contents 



pecies, salt and 



[ of the cells an-anged in twin stellate or lobed 

 masses in each joint (fig. 137, page 204). 

 This stellate appearance arises from the 

 presence of radiating threads, like those from 

 the nucleus of SpiHOCiYUA ; hence it cannot 

 be well observed in dried specimens. Cell- 

 division with previous division of the 

 stellate masses may be well studied in this 

 genus. Kiitzing separates from this genus 

 all the forms in which the spore is formed 

 in the cross branch produced in conjugation, 

 associating them with Zyyoyonium. We 

 prefer to follow Hassall's distribution of the 

 forms, seeing that Zyyoyonium ericetorum 

 is a plant of very different appearance. If 

 the said character is constant, this genus 

 might be divided into two. 



Spores in one of the parent cells. 



Z. cruciata (fig. 137, p. 204). Filaments 

 1-GOO" in diameter; joints equal or twice 

 as long ; spores globose (Hassall, /. c. infra, 

 pi. 38. fig. 1 ; Kiitz. /. c. infra, y. pi. 17. 

 tig. 4). Z. Dilhvynii and stellina of Kiitzing 

 appear to be only smaller states of this, as 

 also Ty7id. lutescens, Hassall, and T.anomala, 

 Ralfs. 



Z. staynalis. Filaments 1-2640" in dia- 

 meter, joints three or four times as long; 

 spores globose or oblong (Hassall, I. c. 

 pi. 38. figs. 9, 10). Tynd. ovalis, Hass., is 

 perhaps a larger form of this. 



Z. insiynis. Filaments 1-1800 to 1-loGO" 

 in diameter, joints twice as long; spores 

 globose (Hass". /. c. pi. 38. figs, 6, 7 ; Kiitz. 

 /. c. V. pi. 17. fig. 1). 



Z. bicornis. Filaments lr440 to 1-200" 

 in diameter, joints twice as long ; spores 

 globose (Hass. /. c. pi. 38. fig. 5 ; Kiitz. /. c. 

 V. pi. 16. fig. 3). 



Spores in the cro.ss branches. 



Z. immersa. Filaments 1-1200" in dia- 

 meter, joints about half as long again; 

 transverse processes very thick, filled by the 

 large and globose spore (Hass. /. c. pi. 39 

 fig. 3; Kiitz. /. c. v. pi. 12. fig. 5). 



Z. conspicua. Filaments 1-1440 to 

 1-1080" in diameter, joints equal or twice 

 as long : transverse' processes long, ventri- 

 cose in the middle, where they enclose the 

 ovate-globose spore (Hass, /. c. pi. .39. figs. 1 

 2: Kiitz. I.e. v. pi. 12. fig. 2). 



Z. decussata. Filaments 1-1440" in dia- 

 meter, joints three times (more rarely fiye 

 times) as long; transverse processes short 



^. 



