S P 1 



[ 241 ] 



S P I 



Linnaeus, order Pulmonariae, class Araeh- 

 nides. The male spider possesses four 

 pairs of legs, the female live, the addi- 

 tional pair enabling her to carry her eggs. 

 The legs are composed of seven joints, 

 the two first forming the hip, the third 

 the thigh, the fourth and fifth the tibia, 

 the sixth and seventh the tarsus. The 

 feet are spread out in diverging rays, so 

 as to include a wide circle, and afford an 

 extensive base of support ; they terminate 

 in two, or, sometimes, in three hooks. In 

 front of the head are placed members 

 resembling feet, having affixed to them, 

 or terminating in, a moveable hook, or 

 pincers, flexed inferiorly, underneath 

 which is a minute opening that permits 

 exit to a venomous fluid contained in an 

 adjoining gland. By the injection of this 

 poisonous fluid the common spider of this 

 country is able to kill a fly in a few mi- 

 nutes, and the large spider of South 

 America can, by the same means, destroy 

 the smaller vertebrated animals, and pro- 

 duce even in man severe constitutional 

 disturbance. The greater number of 

 species possess a curious apparatus for 

 spinning threads, and for constructing 

 nets, for the entanglement of flies and 

 small insects. This net or web is as 

 various as the species, each species con- 

 structing its own peculiar form of net : in 

 addition to the principal web, which is 

 spun out for the capture of small insects, 

 the spider frequently constructs a smaller 

 one, both as a residence and a place of 

 ambush. Between these two constructions 

 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 communicating 

 thread afford information to the concealed 

 spider, who instantly rushes towards his 

 victim and endeavours 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 pos- 

 terior legs next the abdomen. These 

 spines are employed as a carding appara- 

 tus, 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, disen- 

 gaging the web from them. 



Fossil remains of spiders exist in strata 

 of very high antiquity. Prof. Buckland 

 is of opinion that, although spiders have 

 not yet been discovered in the carbonife- 

 rous series, the probability is they did 

 exist at that period. Count Munster has 

 established the existence of spiders in the 



Jurassic portion of the secondary forma- 

 tions. 



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 together, or in separate groups. 

 When the flowers are sessile they form a 

 spike: the plantain, lavender, corn, &c., 

 afford examples. 



SPI'KELET. In botany, the term applied to 

 a subdivision of a spike, forming, as it 

 were, a small spike : by some authors 

 this word is applied exclusively to the 

 spike of grasses. 



SPI'NAL. (spinalis, Lat. spinal, Fr. spinale, 

 It.) Relating to the spine ; belonging to 

 the spine. 



SPINE, (spina, Lat. epine, Fr. spina, It.) 



1. In anatomy, the vertebral column 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. 



3. In zoology, a thin pointed spike. Some 

 of the spines of fishes are simply imbed- 

 ded in the flesh of the animal, and attached 

 to muscles ; 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 greywacke series 

 to the chalk inclusive ; they have obtained 

 the name of ichthyodorulites. 

 SPI'NEL,. > (spinelle, Fr. spinella, It.) A 

 SPI'NELLE. $ species of corundum both of 

 an octahedral and a dodecahedral form. 

 Its colours are red, black, blue, brown, 

 yellow, and white. It occurs in regular 

 crystals, and, occasionally, in rounded 

 grains. It scratches quartz, its hardness 

 being == 8'0. Its structure is usually 

 foliated, with laminse parallel to the faces 

 of the octahedron. Specific gravity from 

 3-5 to 3-8. It is infusible 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 2'57. Sometimes its co- 

 louring matter is oxide of iron instead of 

 chrome. The spinelle ruby is a sub- 

 species. 



SPINE'LLANE. A variety of dodecahedral 

 zeolite. A mineral of a plum-blue or 

 blackish-brown colour, found on the 

 banks of the river Laach, near Ander* 

 nach. It occurs in hexahedral prisms, 

 terminated by three-sided summits, whose 

 faces stand on alternate, but different, 

 lateral edges at each extremity. It fuses 

 easily before the blow-pipe, becoming 

 white, and is converted into a porous 



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