304 Prof. T. Thorell on Dr. Bertkau's 



great and polymorphous tribus TubitelarijB. But in spite of 

 these and other shortcomings, the classification of the Spiders 

 given in my work ' On European Spiders ' has, with or with- 

 out some slight modifications, been adopted by most living 

 arachnologists. 



Very different from this classification, in which the primary 

 groups of the Spiders are distinguished chiefly by means of 

 characters taken from the totality of their external parts, and 

 little notice is taken of their internal or anatomical structure, 

 is a system of classification lately proposed by Dr. Philipp 

 Bertkau* of Bonn ; for not only are the principal groups in 

 this system based on features which are more isolated and 

 by most other authors considered to be of comparatively less 

 importance, but he also gives much attention to the internal 

 parts, and especially to the differences in the structure of the 

 hreathing-organs^ thus approximating to the classification 

 adopted by Dufour. But while Dufourf and, at last, follow- 

 ing him, LatreilleJ divided the Spiders into " Quadripul- 

 monaires''^ and '"'• Bipulvionaires'''' {TetrapneumoneSy Latr., 

 and DiyneumoneSy Latr.), on the ground of the different 

 number, four or two, of their air-sacs or so-called lungs (lung- 

 sacs, lung-books, lamellar trachea3), they are by Bertkau 

 divided into the two suborders Tetrasticta and Tristicta^ the 

 former with four, the latter with three hreathing-holes (spi- 

 racles, stigmata). The Tristicta are further divided into two 

 groups, Crihellata and Meromartxmillata^ of which the former 

 are provided with the spinning-organs known under the names 

 of crihellum (or inframammillary organ) and calamistrum, 

 the latter being devoid of these organs ; the Meromammillata 

 Bertkau divides into Perissonycha, with three^ and Artionycha 

 with two tarsal claws. All these different groups are divided 

 into a certain number of " families," in the characterization 

 of which the structure of the organs of respiration and gene- 

 ration plays in general an important part. To the biological 



biologischen Eiuleitung," in Schriften des naturwissenscLaftliclieii Vereins 

 fiir Schleswig-Holstein, vol. i. 1883). — On tlie systematic position of 

 Pholcus (and Ctenium), see fiu-tlier on. 



* See especially bis "Versuch einernatiirlichen AnordnungderSpinnen," 

 in Archiv fiir Naturgeschichte, sliv. i. pp. 351 et seq. (1878), and his 

 treatise " Ueber das Cribellum uud Calamistrum. Ein Beitrag zur His- 

 tiologie, Biologic und Systematik der Spiuneu," ibid, xlviii. i. pp. 316 et 

 seq. (1882). 



t " Observations sur quelques Arachnides quadripulmonaires," in An- 

 nales generales des Sciences Physiques, vol. v. p. 2G (1820). It is known 

 that Dufour, believing that Dysdera had four air-sacs, erroneously referred 

 that genus to his " Araignees quadripulmonaires." 



J In his ' Families Naturelles du Kegne Animal, &c.,' 1825. 



