302 Prof. T. Thorell on Dr. Berthau's 



in the animals' structure, wliicli, it is true, may sometimes 

 be difficult sharply to define, but which, in general, make it 

 easy to decide to which of the divisions, based on these differ- 

 ences, a spider belongs, even when nothing is known of its 

 habits. 



Concurrently with some classifications in which Spiders 

 were grouped in two or more great divisions, according to 

 differences in their inner (Dufour) or outer (Walckenaer, 

 Blackwall, &c.) structure, several attempts were also made, at a 

 rather early period, to combine the two principlesin question, the 

 structural and the hiohgical, the principal stress being laid on 

 the organization, especially on the modifications of the external 

 parts, the characters taken from the animals' habits and webs 

 being considered less important or auxiliary. Thus the old 

 well-known biological groups were, in general, maintained, often 

 even with the old denominations given to them by Latreille — 

 Orbitela3, Insequitela?, &c. An important step in this direc- 

 tion was made by Sundevall, who, in his " Svenska Spind- 

 larncs Beskrifning "* (Description, of the Swedish Spiders), 

 gave a rather detailed exposition of the characteristics, taken 

 from the external parts, which he considered to distinguish 

 each of the seven " tribus " (Orbitela3, &c.) into which, v/ith 

 Latreille, he divided the Spiders f; the form of the web &c., 

 he mentioned first at the end of the diagnoses of the different 

 " tribus." In his ' Conspectus Arachnidum ' (1833) Sundevall 

 retained, it is true, the same great groups, but he called 

 them " families," and changed their names into Epeiricles, 

 Theridides, Brassides, &c. ; and thus escaped the accusa- 

 tion of having regarded the form of the webs and the mode of 

 locomotion, implied in the Latreillian names, as the distin- 

 guishing characters of the groups adopted. He was followed by 

 Westring, who, in his admirable work ' Araneae Suecicge,' 

 characterized his " families " Epeirida3, Therididfe, &c. still 

 more sharply and more in detail than Sundevall had done. 

 As, however, Sundevall and Westring were but insufficiently 

 acquainted with extra-European spiders (Westring took into 

 consideration only those found in Sweden), the characters of 

 the groups adopted by these authors do not always hold good 

 for the exotic forms, and are in many respects in need of 

 enlargement and other modifications ; but the method of 

 characterization followed by them, and especially by West- 

 ring, is no doubt still the right one, i. e. to give a detailed 

 exposition of {at least) the external parts in each group, 



* K. Vetensliaps-Akademiens Handlingar for Sr 1829, pp. 199-203 

 (1830). 

 t The Territelfe of Latreille he called, however, " Thej-aphoscs (Walck.)." 



