SPOLVERINA. 



[ 721 ] 



SPONGIDA. 



mai^s, and consists of three elements — micro- 

 scopic trabecule, fibres, or bands, parenchy- 

 ma-cells, and the smaller blood-vessels — or 

 of cells and an intercellular substance. The 

 trabecuhv agree in structm'e ^^ ith the larger 

 ones. The tibres or bands are the termina- 

 tions of the sheaths of the vessels ; they are 

 indistinctly fibrous, and free from elastic 

 tissue. The parenchjona-cells resemble 

 those in the splenic corpuscles. Blood-cor- 

 puscles are found enclosed in cells, from 

 one to twenty in each, or surrounded by a 

 transparent substance, their contents exhi- 

 biting vai'ious changes in colour and con- 

 sistence. The arteries tenninate in elegant 

 tufts or peuicilli, becoming continuous with 

 a meshwoi-k of capillaries. 



The blood-corpuscles from the blood of 

 the splenic vein frequently contain crystals 

 of hsematoidine. 



In the examination of the spleen, the tra- 

 beculse aie best seen after washing away the 

 pulp with water, the splenic corpuscles by 

 tearing the spleen or boiling it, either in 

 the pig or ox. The cells containing blood- 

 coi-puscles must be searched for in the pulp 

 unacted upon by water. The muscular fibres 

 are most evident in the smaller trabeculse, 

 especially after treatment A\'ith dilute nitric 

 acid (one part to five parts of water). 



BiBL. Koliiker, Mik, An. ii. and Todd's 

 C'ljcl. An., art. Spleen ; Gray, A, Cooper^s 

 Prize Essay ; Saunders, Goodsir^sAnn.ofAn. 

 1851, i. ; Huxley, Qii. Mic. Jn. ii. 1854 ; 

 Frey, Mikros. ; Miiller, Strieker's Hist, and 

 the Bibl. therein. 



SPOLVERI'NA, Mass.— A genus of 

 ilicro-hchens, parasitic on the thallus and 

 prothallus of various crustaceous lichens. 



Char. Spores 1-2, large, globose-ovoid, 

 simple, colourless, or yellowish. (Lindsay, 

 Qu. Mic. Jn. 1869, 344.) 



SPONDYLOCLA'DIUM.— A genus of 

 Dematiei ( Ilyphomycetous Fungi), analo- 

 gous to Arthrobotryum, characterized by the 

 erect filaments, with whorled multiseptate 

 spores (PI. 27. fig. 15j. (Mart., Fl. erl. 354 ; 

 Link, Spec. 79 ; Hotixaann, Fl. germ. ii. 

 pi. 13.) 



SPONDYLOM'ORUM, Ehr.— A genus 

 of Volvocinese. 



S. quaternarium. Ccenobium globose, 

 compoj^ed of 8-12-10 cuneata green cells, 

 each with a long cilium, and a dorsal red 

 eye-spot, enclosed in a colourless gelati- 

 nous envelope (PI. 3. fig. 23). In ditches. 

 (Pertv, ie6e?2.s/'. 177; Rabenht. ^/y. iii. 98.) 



SPONGASTERIS'CUS, Hckl.— A genus 



of Radio-flagellate Infusoria, with a silice- 

 ous perforated carapace. 2 species; marine, 

 (Kent, Inf. 229.) 



SPON'GIDA or PORIF'ERA.— A Class 

 of Protozoa. 



Char. Form variable ; fixed by a kind of 

 root at the base, or incrusting ; consisting 

 of a soft gelatinous sarcodic mass, mostly 

 supported by an internal skeleton, composed 

 of reticularly anastomosing horny fibres, in 

 or among which are usually imbedded sili- 

 ceous or calcareous spicida ; or sometimes 

 the spicula alone form the skeleton. 



The horny fibres forming the skeleton of 

 sponges, which may be well seen in any 

 common sponge, are cylindrical, and vari- 

 ously united, so as to form a coarse network 

 with roundish or angular microscopic meshes, 

 In addition to these generally diftused 

 meshes or intervals, large (to the naked 

 eye) rounded apertures or oscula are scat- 

 tered over the surface of most sponges, 

 leading into sinuous canals permeating their 

 substance in every direction ; and between 

 these are other smaller apertures, just visi- 

 ble to the naked eye, also the orifices of 

 canals, which traverse the substance and 

 communicate with the oscular canals. 



In the Hving sponge, this skeleton is 

 covered with a glairy or gelatinous, colour- 

 less, amorphous substance, resembling that 

 of which Amoebce are composed; the 

 proportion being variable in the different 

 genera. This substance appears to be 

 composed of minute masses, those on the 

 smfaces being furnished ^vith a long and 

 slender flagellum, or forming collared 

 monads ; and during life, by means of these, 

 water entering by the smaller apertures, 

 and reaching the oscular channels, is ex- 

 pelled from the oscula in ciu-rents, which 

 may be rendered visible by sprinkling a 

 little finely powdered charcoal over them. 

 Hence Clark and Kent refer the Sponges 

 to the Choano-flagellate order of the Infu- 

 soria. 



The fibres of the common Sponges appear 

 to be solid under the microscope ; and when 

 treated with sulphuric acid, they are seen to 

 consist of two parts, an outer tubular portion, 

 which is contracted in length by the acid, 

 and an inner cylindrical thread, which 

 usually becomes elegantly wavy or spiral, 

 frequently protruding from the cavity of the 

 outer portion in broken fibres, and resem- 

 bling PI. 28. fig. 22. 



The spicula are of various forms (PI. 46, 

 lettered figui'es), and either scattered through 



3a 



