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



droctonoida'.) situated In i\\e. fourth abdominal segment, whereas 

 in other scorpions it is, on the contrary, placed in the third of 

 these segments — a peculiarity which in the Butholdas neces- 

 sitates a different origin, from that in other scorpions, of the 

 nerve-stems which go to the two first pairs of air-sacs ; and 

 while the embryos of Pandtnus africanus are developed in 

 separate caeca of the ovarian tubes, and are provided with a 

 long apophysis, proceeding from the mandibles, the embryos of 

 Buthus {occitanus) and of Euscoijnus are devoid of this apo- 

 physis, and perform their whole development in the interior of 

 the ovary itself*. The case is no doubt the same, within the 

 order of Spiders, with the characters derived from the form of 

 the trachese and other internal organs, as with those taken 

 from the external parts, or which have been found in their 

 habits and instincts ; in the same way as there are Orbitelarise 

 that do not construct a web, or only an irregular one, Lycosoidae 

 with only two tarsal claws (for instance Thasyr(ea), Pholcoidss 

 with only six eyes {Spermophora) ^ Theraphosoldge (Thera- 

 phosinas, Auss.) with six spinnerets {Hexathele) or with only 

 six eyes (Masteria), nay even Theridioidffi with only two 

 spiracles {Ctemum), so there mai/ be Thomlsoidas with 

 simple, unramified trachese, Drassolda and Therldloldje with 

 a more highly developed system of tracheas, &c.t 



Scorpionini only tivo genera belong: — 1. Scorpio (with the subgenera 

 Euscorpius, BnfJmSj and Brotheas, and perhaps also Hemiscorpion 

 and Opisthophthalmus), and 2. Telegonus. The Androctonini tbrm 

 a single genus, Androctonus (with the subgenera Prionuriis and Cen- 

 trums). It is therefore quite natural that Prof. Lankester regards 

 Peters's classitication of the Scorpions as a failure, and the genera adopted 

 by him as " in most eases unnecessary, often not even justifiable as sub- 

 genera." On my attempt to develop this classification he says, " Thorell 

 has added a number of genera to the already superfluous list, and has 

 modified Peters's classification in what appears to me to be a retrograde 

 spirit " ; and, further, "Dr. Thorell has carried the formation of genera and 

 subgenera too far." To this I will only reply, that I have never proposed 

 or adopted a svbf/enus, and that I do not understand why Prof. Lankester 

 has done me the honour of mentioning my name ; for as be is of course 

 •well acquainted with the works of all more recent authors in the field he 

 treats of, he cannot be ignorant that other arachnologists, and especially 

 Simon and Karsch, have increased the number of genera adopted by Peters 

 and myself by a great many new ones, and that these authors therefore, more 

 than I, are guilty of having modified the classification of the Scorpions in 

 what Prof. Lankester considers a " retrograde " spirit. By going a little 

 further in the opposite direction, or that now commenced by Prof. 

 Lankester, one will, it is true, sooner and more easily arrive at a solution 

 ne ultra of the problem how to divide the Scorpions into natural families 

 and genera. 



* See, for instance, Metschnikoff, " Embryologie des Scorpions," in Zeit- 

 schrift fiir wissenschaftliche Zoologie, xxi. 1870. 



f I may be allowed here to mention a reason against laying, in the 



