ARACHNIDA. 



451 



by a pectoral elongation ; two maxilla-, formed of the basal joint of two small feet 

 or palpi*, or of an appendage or lobe of the same joint; a piece concealed beneath 

 the mandibles, and called the sternal tongue by Savigny in Phalangium copticum, 

 and which is composed of a beak-like prominence, produced by the union of a very 

 small epistome or clypeus, terminated by a very small triangular upper lip, and ot 

 a longitudinal lower rib (carlne) generally very hairy. These, together with the pieces 

 called the mandibles, generally constitute, with certain modifications, the mouth of the 

 majority of the Arachnida. The pharynx f is placed in front of a sternal prominence, 

 which has been considered as a lip, but which, from its situation immediately in front 

 of the pharynx, and from being destitute of palpi, is rather a tongue. The legs, like 

 those of the Insecta, are generally terminated by two small hooks (ungues) and 

 sometimes by an additional one, and all are annexed to the thorax (or rather 

 cephalothoriix), which, except in a few species, is only composed of a single piece, 

 and very often intimately united to the abdomen, which is soft or but weakly 

 defended in the majority. 



With respect to their nervous system, the arachnida remarkably differ from the 

 Crustacea and Insecta, for, if we except the Scorpions, which, in consequence of 

 their articulated tails, have some extra ganglions, the number of these knots does 

 not exceed three, and even in those animals there are only seven. 



The majority of the Arachnida feed upon insects, which they seize alive, or upon 

 which they fix themselves, and from which they suck their juices. Others live as 

 parasites upon the bodies of vertebrat.il animals. There are, however, some which 

 are found only in flour, cheese, and upon various vegetables. Those which sub- 

 i-t upon other animals often increase in a very great degree. In some species two 

 of the legs are not developed before a change of skin, and in general it is not 

 until after the fourth or fifth moulting that these animals become fitted for repro- 

 duction. + 



Those species which have pulmonary sacs§, a heart with very distinct vessels, 

 and six or eight eyes, compose the first Order, Arachnida pulmonaria. 



The others respire by trachea?, and do not possess organs of circulation ; or, if 

 they be present, the circulation is not complete. The tracheae are divided near their 

 origin into different ramification-, mid do not form, as in the Insects, two canals, 

 running parallel with the entire length of the body, and receiving the air in its 

 different parts by numerous breathing pores. Here we can only distinctly perceive 

 two|| at most, situated near the base of the abdomen. The number of the simple 

 eyes is tour at the most. These form our second and last Order, Arachnida 

 trachearia. 



• 1 hese organ* do not differ from true legs, except in their tar.l, 

 \ single Joint, ami generally lenr.inilcd by a small hook, 

 Cri utcea. These maxilla and 

 palpi appt u ml with the palptgcjoofl mandlblea of the 



. ., and to the two I Llmulisa i tho four follow- 



ing i. . iv apps ndago, mi 



in tin foui ' ■ by me in in y 



- iph of 'in French Phalaiiguv, yean in fori Sasigne'i M 

 kin published. Hence it li toey to iciir all Umm articulated 

 UlinteJ Arachnida arc not a kind 



of Crust ucnus ■nttnals, ilrstitute of a head, as Savigny says. 



f M. Btraoaa oitd mvaell hswtooss. Ice, although 



Savigny .nliiiiu (but, a. il . iiunrrcclly) two. 



j W. iota that the Argulu. docs no( att-itn thi* power 



until alter the sixth umult. The name fact la also applicable to 



Lepidoptcroui Insects, and probably to Othtn which ehange tl.elr 

 skins several times — thus, Caterpillars moult four lime, 

 assuming the chrysalis SUM, which If effected by a 61th moult, and 



Kt does not become an imago until alter an 

 its moulting*. 



) Sae. inclosing aerial branehix. or performing ' mugs, 



and which I distinguish from the latter organ, by la ' <»ou- 

 brain bias. 



| The I'veii.igoiii.les .re destitute of ipll I 



ru.taeca. such as • «"d "<«" 



Km traea suelor.a. - '" lh * 



.. trust.., r,. from whit 



the strueturcnl the Booth, Ik * »•" 



■ :„ , , , ,i„. ,'halangtum, eousldenng 



they may respire by the »"■ I ahlsV. 



