REPORT ON ZOOLOGY. 203 



the number of genera to sixty-nine, but in the opinion of Duges 

 many of these rest on doubtful if not erroneous characters. 

 Leon-Dufour, Audouin, and De Theis have all contributed me- 

 moirs to the Ann. des Sci. Nat. on particular genera*. Accord- 

 ing to LatreiUef , this last gentleman is engaged in a new work 

 on these animals, to be illustrated by plates. 



The most important group among the Pulmonary Arachnida 

 is that of the Araneidee. Nevertheless, like all the others in this 

 class, it has been greatly neglected. Walckenaer, Latreille, 

 and Leon-Dufour in France, De Hahn in Germany, and Mr. 

 Blackwall in our own countiy, are almost the only individuals 

 who have given it any attention of late years. Walckenaer, who 

 has studied it most deeply, and whose Tableau des Aran^ides, 

 published in 1805, has been hitherto the only guide for naturalists 

 in this department, has recently proposed a new arrangement of 

 these animals in a memoir read to the Entomological Society 

 of France j. The principal groundwork of his system is the 

 same as in his Tableau, and he still adopts the two large divisions 

 of Theraphoses and Araignees, founded upon the position of the 

 jaws with respect to the rest of the body, and the articulation of 

 the mandibles. The number and position of the eyes serve 

 afterwards for characterizing some well-marked groups subordi- 

 nate to these two large tribes. Walckenaer observes that the 

 species of Spiders have been greatly overmultiplied, from suf- 

 ficient regard not having been paid to the changes incident to 

 different ages with respect to size and colour. Leon-Dufour 

 has more particularly occupied himself with the structure and 

 internal anatomy of the Araneidee. He is the author of some 

 important memoirs§ on this part of the subject, in one of which 

 he has instituted a new division of this group into the two sec- 

 tions of Tetrapneumones and Dipneumoiies, founded on the 

 number of pulmonary sacs, which he was the first to discover 

 are double on each side of the abdomen in certain species, amount- 

 ing to four in all. The Tetrapneumones, which comprise the 

 Th4raphoses of Walckenaer, as well as a small portion of his 

 Araignees, form the subject of a memoir in the Nouv. Ann. du 

 Mus.\\ by Latreille, who speaks highly of this new principle of 

 arrangement. He thinks that it will serve as an immutable 



• Ann. des Set., torn, xxv., xxvi., and xxvii. f Cours d'Entom., p. 546. 



X An extract from this memoir will be found in L'Institute, 1833, No. 18. 

 M. Walckenaer has also lately commenced the publication of a work entitled, 

 Les Araneides de France classees par lettr Organisation, 8fC. (L'Instit. 1834, 

 No, 53.) 



S Ann. des Scien. Physiques de Bruxelles, torn. v. and vi. i| torn. i. p. 61. 



