SIPHONOSTOMA. 



[ 578 ] 



SKIN. 



pinnately branched, producing two- or four- 

 ciliated zoospores in the extremities of the 

 branches. Marine. 



III. Vaucheria. Filaments green, more 

 or less branched, continuous, producing in 

 their apices large solitary zoospores covered 

 with cilia; also bearing lateral globose spo- 

 rangial cells, and hook-like antheridial cells 

 ("horns"). Marine or aquatic, and still 

 more commonly on muddy ground, damp 

 garden-pots, &c. 



IV. BoTRYDiUM. Frond a spherical 

 green vesicle seated on a ramified filamentous 

 base, the cavity of the whole continuous, 

 the ramified base producing new vesicles 

 (sporanges) by stoloniferous growth. Mul- 

 tiplied by the granular contents of the vesicle 

 discharged by a rupture at the summit. On 

 damp (mostly clayey) ground, subject to 

 floods. 



V. Hydrodictyon. Frond a green 

 bag-like net, with usually pentagonal open 

 meshes, formed of cylindrical cells connected 

 by their ends. Reproduced by ciliated zoo- 

 spores formed in the "link"-cells, uniting 

 together and forming a perfect miniature net 

 before escaping from the parent-cell. 



VI. AcHLYA. Filaments colourless or 

 light bro\Miish (like the mycelia of Fungi), 

 free, slightly branched ; producing numerous 

 biciliated zoospores in the apices of the fila- 

 ments, and spores in globose lateral sporan- 

 gial cells. On dead flies, fishes, or some- 

 times on decaying vegetable matter in water. 



BiBL. See the genera. 



SIPHONOSTOMA (Parasita, or Pcecilo- 

 poda). — An order of Crustacea. 



Char. Body often almost entirely enclosed 

 in a buckler, consisting generally of one, 

 sometimes of two pieces ; mouth suctorial ; 

 legs formed for walking or prehension, or 

 partly branchiferous and fitted for swimming. 

 Parasitic upon fishes, &c. 



These animals (PI. 14. figs. 1, 23, 24, 36, 

 and PI. 15. fig. 1), which often present the 

 most extraordinary forms, are found mostly 

 afiixed to the gills of fishes by means of 

 books, arms, or suckers, arising from or 

 consisting of modified foot-jaws. In some, 

 the cephalothorax is distinct from the abdo- 

 men, and the head is more or less distinct 

 from the thorax ; whilst in others the body 

 presents more of a worm-like form, is occa- 

 sionally ringed or segmented, and sometimes 

 exhibits simple or branched lateral lobes or 

 processes. The antenna3 are mostly rudi- 

 mentary. Flattened elytriform dorsal ap- 

 pendages are sometimes present. The ros- 



trum is conical, tubular, and furnished with 

 two setaceous or styliform mandibles. The 

 alimentary canal is straight, without a gas- 

 tric expansion, and its orifices at the two 

 ends of the body. In some, branchial plates 

 form the respiratory organs, but in most the 

 same office is performed by the skin. 



The sexes are distinct, although they are 

 not known in all the species. The males 

 are smaller than the females. The ova are 

 often attached to the lower part of the body 

 of the females, either contained in external 

 ovaries, or simply glued together by the 

 secretion from a special gland, and forming- 

 long, cylindrical, straight or convolute ap- 

 pendages. The young animals have but few 

 legs, swim freely, and frequently resemble 

 the young of Cycloiis. 



BiBL. Baird, Brit. Entomostr. ; M. Ed- 

 wards, Hist. Nat. Crust, iii. ; Siebold, Ver- 

 gleicli. Anat. 



SIROCROCIS, Kiitz.— Probably the my- 

 celium of a fungus. 



BiBL. Kiitzing, Sp. Alg. p. 153. 



SIROGONIUM, Kiitzing. S. notahile 

 =■ Mesocarpiis notabilis, Hass. ; S. sticticum 

 := Spirogyra {Zygnema, Hassall) sticti- 

 ca ; S. breviarticulatum = Spirogyra cur- 

 vata. 



SIROSIPHON, Kiitz.— A genus of Os- 

 cillatoriace£e(ConfervoidAlg8e), which should 

 perhaps have been placed under the older 

 name of Hassallia. This genus is j^rinci- 

 pally distinguished by the solitary branches 

 passing off" from the sides of the rather rigid 

 filaments, the branches arising from longitu- 

 dinal division and lateral growth of intersti- 

 tial cells. The plants are found on wet 

 moors, rocks, &c. Two species seem to be 

 established, — S. ocellata (PL 4. fig. 12), and 

 S. compacta ; others appear doubtful. 



BiBL. Hassall, Brit. Fr. Alg. p. 231. pi. 

 77, 78 ; Kiitzing, Spec. Alg. p. 315, Tab, 

 Phyc. ii. pi. 36, 37. 



SIZYGITES. See Syzygites. 



SKIN or INTEGUMENT OF AnIMALS. 



Three parts are distinguishable in the skin : 

 an outer or cellular, forming the epidermis ; 

 an inner fibrous, or cutis vera; and an inter- 

 nal or subjacent, known as the subcutaneous 

 cellular tissue. The two former constitute 

 the skin proper. 



The cutis vera or corium (fig. 646 c) con- 

 sists of areolar and elastic tissue, with fat- 

 cells, blood-vessels, nerves, absorbents, and 

 unstriated muscular fibres. The fibres of 

 the areolar tissue are variously interlaced 

 and united into interwoven bundles, form- 



