KONGL. SV. VET. AKADEMIENS HANDUNGAR. BAN'1). 13. N:() 5. 7 



careiis, deiisc ciiierasceuti-pilosus, in fuudo pi(u;us, parte cephalica antice rufesrenti. iSternum iiigruin, imniacu- 

 latuin; labium »igium, apict: testaciHini. Area ocniorum ') medioruni proclivi, rectaiifiula, certe non latior antice 

 (juam postice, pauUo lon{i;ior quain latior; oculi medii postici, majores cpiam medii antici, inter se spatio distant, 

 (juod oculi diainetrum itquat; intervalluin inter oeulos inedios anticos evidunter, vix vero dimidio, majus est 

 (|uain diameter horniu oculorum. Mandibulce testaceo-rnfescentes, apice nigrae. Mdxillct nigric, apiee intus ti- 

 stacctC. Palpi rufescenti testacei, minus distincte fusco-annulati. Pedes testacei, nigro-anuuiati : femora magis 

 rufescentia, vix distincte annulata, postica tamen apice infuscata: patellae apice plus minus infuscatie; tibiie basi 

 angusto, apice late nigrte, et pvitterea annulo nigvo angusto versus medium; metatarsi anuulum apicalem latum 

 et aliuin fere medium angustum liahent, spatio angusto disjunctos; tarsi apice nigri. l:mi paris pedes 20, 4:ti 

 17' ., millim. longi; tibia euni patella 4;ti paris 6' 4 millim. Abdomen triangulo-ovatura, bumeris in tubercula 

 duo m.igna, obtusa elevatis; supra obscure einereo-fnscum, serie macularnm testacearum in medio antitM', una 

 oblonga, antc tubercula sita, secuuda parva, in medio inter ea, tertia majore, paullo poue priorem ; mox pone hane 

 macnlam, parum ante medium dorsi, /\ parvum cinereo-albicans, apice abruptum adest, et tum niaeula una alterave 

 parva pallida. Pars posterior dorsi utvinque serie linearum brevium, obliquarum, nigrarum (inter se verisirailiter 

 saepe in lineam flexuosam conjunctarura) limitatur; latera abdominis superius vitta sub-cinerea iniequali occupantur. 

 Venter, qui tuberculis pone vulvam caret, nigricans est, maculis duabus majoribus flavis, fere in medio inter 

 rimam genitalera et anum positis. Vulva ex scapo longissimo et corpore eonstat: corpus tvansverse cordi-forme 

 fere, lateribus rotundatis, ad maximam parteni nigrum, subter (postice) impressione longitudiuali latissima et 

 profunda in duas partes vel lobos divisum, ad apicem rectura fere angulum inter se formantes; scapus basi latus, 

 repente posteriora versus flexus, fere -formis, transverse striatus, testaceus, basi et apice angustato-obtuso in- 

 fuscatis. — Mas iguotus. 



') Simon (Arau. nouv. ou pen coiiiins etc, 2' Méin., p. 5 et .se(|.) lias proposed a theory respecting the eycs of spiders, whicli 

 plays an importiiiit part in his iiew classification of these animals, and which, if it should be found to be correct, will bc of 

 the greatest intere.st. He in faet distingnishes in spiders tvvo separata kinds of eyes, dnij-eyes (ycu.x diurnes) and niijht-eyes 

 (yeux nocturues), and of thcse, "day-eyes" oiily are fonnd in his Oculatce ( CHigradm and Saltigradce), whereas ouly "night- 

 eyes" occnr in his Gnapliosai (Dysderoidm and Seyiodinie]: of what kind the eyes are in the Theraphosce, he does not state; in 

 Simon's AraneiK, with but few exceptions, eyes of both sorts are said to be inet with, and it is in these cases only the anterior 

 eentral eycs that are day-eyes, the remaining six being night-eyes. The day-eyes differ from the night-eyes by the former 

 being "colorés ct convexes", the latter "plats et d'un blanc brillant": on the colour however Simon does not appear to lay any 

 especial weight, as he says of the eyes of the Oculntai, that they are "tons sembables par leur nature et du type diurne, bien 

 que la couleur de leur cornée" (choroideV) "soit tri;s-variable". This is certainly quite trne: in mauy Attoidie for example, the 

 large anterior eyes are, as is known, of a brilliant vvhite colour, and the eyes of these spiders are without a donbt intended 

 to see with by day; in Jelskin unicolor Tacz. the two large anterior eyes are of almost water-like transparency, whereas the 

 six posterior eyes are black. It must then, strictly speaking. be the greater or less degree of convexity that forms the distinc- 

 tion betvvcen day-eyes and night-eyes. Sometimes, as in the case of Agalena, if is however, according to Simon, difficult to 

 distinguish between day-eyes and night-eyes, and this is probably also the case with Epeira, Linyphia, Erigone, Theridiiim and 

 several others of Simon's Arnneai, iu which, as far as 1 can see, it is in general not the two anterior middle-eyes alone that are 

 convex. It is moreover not very easy to see why the more convex eyes should be more serviceable to see with by day, anil 

 the flat eyes better adopted for night-vision: it seeras a more natural idea. that eyes with a strongly convex cornea serve better 

 to see near objects, while the less convex cornea is calculated for more distant vision. (In spiders, in fact, the cornea itself 

 serves as a refracting lens.) This surely offers a reason why the two anterior central eyes, which are situated nearest to the 

 niouth, are in general very convex. — According to Simon, it is the two anterior central eyes, the day-eyes, which are missing 

 in ö-eyed spiders: but is this also the case in, for example, Segestrinf The two hinder central eyes are sometimes, as in mauy 

 DrnssoidcE and in (Kcobius, much tlattened, and so unlike the other eyes, that one raight be tempted to look upon them as 

 either not yet perfectly developed, or as already under process of reduction: their fnnction as organs of sight in CEeobius has 

 even been doubted (by C.*.mbrii)G1£). In Sesticus speluncarum Pav. and Leptoneta microphthnlma Sim. both the anterior and 

 posterior central eyes have disappeared. 



It is to be wished that Simon would somewhat raore accurately describe the researches on which his views aregrounded: 

 his theory is in fact so much the more remarkable, as no previous naturalist, who has iuvestigated the finer structure of the 

 eyes of spiders, appears to have been aware of the existence of any distinction between day-eyes and night-eyes. Walckenaer 

 indeed, as Simon remarks, believes that in spiders two different species of eyes may be distinguished, namely those which 

 exhibit "uue sorte de prunelle", and others which are "plus simples" (H. N. d. Ins. Apt., I, p. 113); but he considers the 

 former as adapted for more distant vision, and the latter as serving to distinguish very near objects. Simon considers these 

 two kinds of eyes as corresponding to his "yeux diurnes" and "yeux nocturnes" respectively, but this would seem to vequirc 

 some explanation, especially as Walckenaer does not mention either different convexity or different colour as a criterion to 

 distiuiiuish between them. 



The eyes of spiders, like those of other Arthropoda, pi'esent, beneath the cornea ("lens"), a layer of staff-shaped bodies 

 which terminate in a club-like gelatinous knob: these bodies, which correspond to the stratum bacillosum of the retina in 

 higher animals. and form the perceiving apparatus of the eye, are surrounded by a more or less dark-pigmented choroid. The 

 refracting cornea itself, which is formed of a continuation of the external, chitinous covering of the body, is, in spiders, common 

 to the whole bundle of staves, and strongly convex inwards. In many spiders the choroid exhibits a differently coloured 

 tapetum, frequently with a metallic lustre (as e. g. in the eyes of fish): Leydig (Zum feineren Bau d. Arthropoden, in Mi ller's 

 Archiv f. Anat. u. Physiol., 1855, p. 441) mentions such a tapetum in some species of the genera Epeira, Tetragnatha, Erigone, 

 Theridiuvi, Tegeiinria, Amnurobius, Argyronetn. "wo es stark wciss spiegelt", Dysdera, Lycosn. The choroid also generally con- 

 tains muscular tibrcs, on the contractions of which the jerking motion observable in the depth of the eyes in many spider.- 

 depends. In the large eyes of the Attoidm these (ibres even form a belt-like "iris" round the cornea. I suppose it is eyes of 

 this descriptiou that Walckenaer means when he speaks of eyes provided "with a sort of pupil '. — On the eyes of spiders 

 conf., besides Leydig's works, Dujardin, Mém. s. les veux simples ou stemmatcs d. Anini. arfic. in Ann. d. Sc. Xat.. 5 Sér.. 

 1867, T. VII, pp. 104—112. 



