p I 



[412] 



S P I 



both as a residence and a place of 

 ambush. Between these two con- 

 structions there is placed a thread 

 of communication, and no sooner 

 is the struggling insect involved in 

 the meshes of the larger net than 

 the vibrations of this communica- 

 ting thread afford information to 

 the concealed spider, who instantly 

 rushes towards his victim and en- 

 deavours to destroy it, by piercing 

 it with his dart and infusing into 

 the wound his poisonous fluid. The 

 web is produced by a double series 

 of spines, opposed to each other, 

 and planted on a prominent ridge 

 of the upper side of the metatarsal 

 joint, or that usually regarded as 

 the first joint of the foot of the 

 posterior legs next the abdomen. 

 These spines are employed as a 

 carding apparatus, the low series 

 combing, or extracting the ravelled 

 web from the spinneret, and the 

 upper series, by the insertion of its 

 spines between those of the other, 

 disengaging the web from them. 



Fossil remains of spiders exist in 

 strata of very high antiquity. 



SPIKE, (spica, Lat.) In botany, a 

 species of inflorescence, in which 

 the flowers stand sessile along a 

 common peduncle, and are either 

 placed alternately and crowded to- 

 gether, or in separate groups ; the 

 plantain, lavender, corn, &c., afford 

 examples. 



SPI'KELET. In botany, the term ap- 

 plied to a subdivision of a spike, 

 forming, as it were, a small spike. 



SPINE, (spina, Lat. epine, Fr. sp'ma, It. ) 



1. In anatomy, the vertebral co- 

 lumn or back-bone of vertebrated 

 animals. 



2. In botany, a sharp point, or 

 thorn; the spines of plants differ 

 from prickles, inasmuch as they 

 proceed from the wood of the plant, 

 whereas a prickle comes from the 

 bark only, and they are distin- 

 guished by their woody vascular 

 centre. 



3. In zoology, a thin pointed spike. 

 Some of the spines of fishes are 

 simply imbedded in the flesh of 

 the animal, and attached to mus- 

 cles; others are articulated with 

 bones which lie beneath them. 



4. The word spine is occasionally 

 used to signify a ridge. 



The fossil spines of various fishes 

 are found in strata from the grey- 

 wacke series to the chalk inclusive ; 

 they have obtained the name of 

 ichthyodorulites. 



SPI'NELLE. } (spinelle, Fr.) A species 

 SPI'NEL. ) of corundum both of an 

 octahedral and dodecahedral form. 

 Some mineralogists place spinel in 

 the Ruby family. Its colours are 

 red, black, blue, brown, yellow, 

 and white. It occurs in regular 

 crystals, and, occasionally, in 

 rounded grains : when crystallized, 

 it is found either in regular octa- 

 hedrons, occasionally having their 

 edges replaced, or in macles, pre- 

 senting very different forms. It 

 scratches quartz, its hardness being 

 = 8. Its structure is usually fo- 

 liated, with laminae parallel to the 

 faces of the octahedron. Specific 

 gravity from 3*5 to 3*8. It is in- 

 fusible before the blow-pipe, and 

 intense heat does not even deprive 

 it of its colour. It consists of 

 alumina 82-47, magnesia 8'78, 

 chromic acid 6.18, loss 2 '5 7. 

 Sometimes its colouring matter is 

 oxide of iron instead of chrome; 

 the red specimens containing chro- 

 mic acid; the blue, protoxide of 

 iron. The spinelle ruby is a sub- 

 species, of a scarlet colour; the 

 rose-red specimens are termed Ba- 

 las rubies ; the yellow, or orange- 

 red, spinel is called Rubicelle; and 

 the violet coloured, Almandine 

 ruby. Spinel ranks as a precious 

 stone, and is worked by the lapi- 

 dary for ornamental purposes. As 

 a species, spinel was first estab- 

 lished by Rome de Lisle and Wer- 

 ner, and by them separated from 



