NA TURE 



281 



THURSDAY, FEBRUARY lo, 1876 



OLD AND NEW WORLD SPIDERS 

 Descriptions of Several European and North-African 

 Spiders. By T. Thorell. Kongl. Svenska Vetenskaps. 

 Akademiens Handlingar, Bandet 13, n. o. 5, pp. i — 203. 

 (Stockholm : Norstedt and Soner, 1875.) 

 A Collection of the Arachnolo^ical Writings of Nicolas 

 Marcellus Hentz, M.D. Edited by Edward Burgess. 

 With Notes and Descriptions by James H. Emerton. 

 Forming No. II. of Occasional Papers of the Boston So- 

 ciety of Natural History, pp. i — 171, PI. i — z\. (Boston: 

 U.S.A., 1875,) 



IT is a somewhat singular coincidence that the two 

 works at the head of this article should have been 

 published just about the same time. We shall endeavour 

 briefly to show the value and bearing of each. 



It is probably undeniable that an illustrated book on 

 any branch of natural history is more acceptable to 

 the public — certainly more attractive — than one wholly 

 devoid of pictorial illustrations ; and not without good 

 reason, for it is well known what great assistance even 

 the advanced student obtains from a single glance at an 

 illustration, when traced by a hand well cognisant of the 

 point sought to be illustrated, even though the hand may 

 be entirely wanting in artistic power. The want, however, 

 of drawings to assist the comprehension of the dry details 

 of natural objects may be reduced to a minimum by the 

 presence of good diagnoses. Pleasant are those pages 

 where both these helps exist ; dreary and uninviting indeed 

 (though sometimes inevitable) are long and dry details of 

 form, structure, and colour, when unenlivened either by 

 drawings or diagnoses. From such dreariness Dr. Tho- 

 ell's two hundred quarto pages of descriptions of spiders 

 inder the title given at the head of this notice) are 

 ived by the excellent diagnosis with which each descrip- 

 iion is preceded. It not unfrequently happens that a 

 diagnosis is a mere formal abstract of the longer descrip- 

 tion that succeeds it ; this is, however, not the case in the 

 present instance, where each diagnosis puts before us just 

 such distinctive points of special form, structure, and 

 colour as the describer, were he at all able with his pencil, 

 \vould endeavour to delineate by means of rapid sketches 

 and dissectional drawings. 



In respect to this point Dr. Thorell remarks (p. 4), that 

 he has " prefaced his descriptions with diagnoses^ although 

 this is not done by the generality of modern arachnolo- 

 gists," it is, he says, " my firm conviction that tolerably 

 good diagnoses very greatly facilitate the determination 

 of unknown species, even though they be not real [by the 

 term real Dr. Thorell appears to mean /"«//] definitions." 

 This places a diagnosis, in relation to the full description, 

 exactly on a par with the part delineation and dissectional 

 drawing when compared with a full artistic illustration ; 

 neither the diagnosis nor the dissectional drawing, how- 

 ever characteristic, precludes the necessity for a full 

 description, nor for a full artistic illustration where it can 

 be had ; in fact, were it not a serious question of space 

 and cost, amounting often to a positive bar, no natural 

 object could be said to be well and properly described 

 and illustrated without a diagnosis., such as that mentioned 

 Vol. XIII. — No. 328 



above, a fill description embracing an almost photo- 

 graphic accuracy of every part, and (where closely allied 

 forms exist) a differential description as well, besides full, 

 and dissectional drawings. Of course the full description 

 would be broken up into ordinal, family, generic, and 

 specific characters, each in their proper place ; the three 

 first only requiring repetition where, in the individual 

 examples, they happened to depart from the strict type. 



The introductory pages of the work before us are in 

 English, while the descriptions are in Latin ; and the 

 materials from which Dr. Thorell has drawn them up 

 have been gathered from various collectors and widely 

 distant parts of Europe, including the northern shores of 

 Africa ; which last, under the term " Mediterranean 

 Basin," Dr. Thorell rightly joins to Europe as a single 

 zoological province. 202 species, belonging to 5 1 genera, 

 distributed among 12 families, are described, 24 of the 

 species being given as new to science ; a large proportion 

 of the remainder, together with four new genera, having 

 been published as new but a short time before, under 

 the title " Diagnoses Aranearum Europasarum aliquot 

 Novarum Scripsit." T. Thorell, in Tijds. voor Entom. 

 Deel. xviii., 1875. 



Dr. Thorell states (p. i) that he follows here, with some 

 slight modifications, the classification proposed in his 

 former work " On European Spiders ;" this mention gives 

 rise to a long foot-note, of two closely-printed pages, in 

 which he examines and criticises M. Eugene Simon's 

 strictures of his system (published in "Aran. Nouv. ou 

 peu Connus du Midi de I'Europe," 2* Mdm. ; " M^m. Soc. 

 Roy. de Sciences de Liege," 2* ser. t. v., 1873). It is not 

 necessary to enter here into the merits of this little pas- 

 sage of arms, but we come to the conclusion, on perusing 

 it, that Dr. Thorell is probably right in saying that he 

 " has not been so fortunate as to make himself under- 

 stood " by M. Simon. At page 7, the latter author's theory 

 respecting the eyes of spiders is discussed in another 

 long foot-note. This theory has already been noticed 

 in these columns (vol. xi., p. 224). Dr. Thorell, 

 while entering fully into the question of the real 

 nature and structure of the eyes of spiders, says, with 

 regard to this theory, that " it is to be wished that M. 

 Simon would somewhat more accurately describe the 

 researches on which his views are founded ; his theory is, 

 in fact, so much the more remarkable, as no previous 

 naturalist who has investigated the finer structure of the 

 eyes of spiders, appears to have been aware of the ex- 

 istence of any distinction between day-eyes and night- 

 eyes." Independently, however, of M. Simon's theory, 

 the question as to the nature of spiders' eyes is a very 

 interesting one ; and very valuable would be those re- 

 searches which should reveal to us the actual anatomical 

 condition of such eyes as, for instance, the apparently 

 atrophied, and probably useless, ones of the hind-central 

 pair in the genus Oecobiits, Luc. 



A footnote of considerable length is appended to pages 

 66 and 67 on the venom of various species of the genus 

 Lathrodecttis, comparing it with the reputed venom of 

 Galeodes araneoides, and questioning the correctness of 

 M. Simon's conclusions (Mem. Soc. Roy., Lidge, 2 ser. 

 t. v.), that the bite of Lathrodectus lygiittatus is not 

 poisonous. Another point, also of great interest, is noted 

 at p. d'^y where Dr. Thorell speaks of traces of segmenta- 



