ZOOTEIRA. 



[ 827 ] 



ZYGNEMA. 



Spermatozoids are transitory structures; 

 when discharged from the parent cell, they 

 either make their way 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 SPERMATO- 

 ZOIDS, these bodies vary much in form. In 

 the higher Cryptogamia they are spiral fila- 

 ments (PI. 40. figs. 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 VAUCHERIA, among the Con- 

 fer voids, are also biciliated globules with 

 the cilia fore and aft, while those in SPH^E- 

 ROPLE^E resemble the microgomdia of this 

 family, having their pair of cilia on the beak ; 

 in (EDOGONIUM they resemble the zoospores, 

 but are smaller. The latter observation is 

 in favour of the microgonidia of Hydrodic- 

 ti/on, &c. being spermatozoids. 



ZOOTEI'RA, Wright. A genus of Ac- 

 tinophryina (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, Pritchartfs Infusoria, 

 563. 



ZOOTHAM'NIUM, Ehr. A genus of 

 Vorticellina (Peritrichous Infusoria). 



Char. Body like Vorticetta, usually of 

 different shapes, attached to the ends of 

 a branched zoary ; internal muscle branched 

 and continuous. Many species, salt and 

 fresh water. 



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

 of polypidom racemose-umbellate, bodies 

 white, stalks very thick. Freshwater; 

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



BIBL. Ehr. Infos. 288 ; Stein, Inf. ; Clap. 

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



ZOS'IME, Boeck. A genus of Copepoda. 

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

 ii. 14.) 



ZOS'TERA, L. A genus of Monocotyle- 

 douous Flowering plants (Nat. Ord. Zostera- 

 ceae), growing in sea-water ; remarkable for 

 the POLLEN, of which the grains are repre- 

 sented by tubular filaments destitute 01 an 

 outer coat and exhibiting ROTATION when 

 fresh. 



ZYGNE'MA, Agardh, in part (Tynda- 

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

 maceae (Confervoid Algae), consisting of 

 filamentous plants, with the green contents 



| of the cells arranged 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 



i the nucleus of SPIROGYRA ; hence it cannot 



j be well observed in dried specimens. Cell- 



| division with previous division of the 



i 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 Zygogonium. We 



prefer to follow HassaU's distribution of the 



forms, seeing that Zygogonmm 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. crimata (fig. 137, p. 204). Filaments 

 1-600" in diameter ; joints equal or twice 

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

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

 fig. 4). Z. Dttlwynii and stellina of Kutzing 

 appear to be only smaller states of this, as 

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

 Ralfs. 



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

 meter, joints three or four times as long ; 

 spores globose or oblong (Hassall, /. c. 

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

 perhaps a larger form of this. 



Z.insignis. ^ Filaments 1-1800 to 1-1560" 

 in diameter, joints twice as long; spores 

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

 I.e. v. pi. 17. fig. 1). 



Z.bicornis. Filaments 1-440 to 1-200" 

 in diameter, joints twice as long; spores 

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

 v. pi. 16. fig. 3). 



Spores in the cross toanches. 



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

 meter, joints about half as long again; 

 i transverse processes very thick, filled by the 

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

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



Z. compicua. 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 



meter, joints three times (more rarely five 

 j times) as long; transverse processes short 



