Phylogevy of the Arachnida. 311 



and Plialangicla3 (unquestionable forms) first occur in the 

 Cenozoic deposits (Zittel, he. cit.^ adapted from Scudder). 

 As I previously stated, it appears to me very probable that 

 the Arachnida have divided into two branches ; of these the 

 one with the Scorpions at its extremity served to give rise to 

 the Pedipalpi and the Aranese, while from the other, in which 

 forms standing midway between the Pseudoscorpions and the 

 Solifugse belong to the more primitive types, arose the rest of 

 the Arachnida *. In the case of the former group there 

 exists in the embryonic or even in the postembryonic period 

 a distinctly segmented postabdominal division, while the 

 function of respiratory organs is discharged by lungs (meta- 

 morphosed branchia3) and partly by modifications of these 

 organs (Dipneumones) ; in the latter no postabdominal 

 division can be distinguished (with regard to Ghelifer^ cf. 

 No. C6, pp. 157-158), the respiratory organs are represented 

 exclusively by tracheas, which moreover are not infrequently 

 dendriform, while in many cases the stigmata are situated in 

 the cephalothorax. 



As to the mutual relations of the various orders in each of 

 the groups mentioned, but especially in the second, we can in 

 the present state of our knowledge of their development only 

 form a partial judgment. In the first group the AranejB, in 

 the second the Acarina, are most divergent ; in this way the 

 relation of the Arane^e to the Scorpions in the first group is 

 the same as that of the Acarina to the Pseudoscorpions and 

 the Solifuga3 in the second. If we disregard the little-studied 

 Cyphophthalmida3 (and Gihhocellum)^ we may regard the 

 Phalangidffi as a branch of the primitive stem of the second 

 group of Arachnids, which separated at a very early period ; 

 their ancestors were probably very closely allied to certain 

 Anthracomarti (families Architarbida^ and Eophrynidge) f of 

 the Coal-measures. 



* The position of the Tardigrades is, as it seems to me, still altogether 

 indefinite {cf. the parallels between the Tardigrades and Insect larvae, as 

 stated by von Kennel, No. 27). 



t The order of Arachnids that occurs in the Coal-measiu-es, the 

 Anthracomarti of Scudder, is apparently an altogether artificial group. 

 This is already indicated by the too con.>iderable difference in the number 

 of the abdominal segments in the various representatives of the group (in 

 certain cases four, in others as many as nine), while a comparison of the 

 various views on the subject of the Anthracomarti also leads to the same 

 conclusion. Karsch (No. 23, p. 558) assumes, on the basis of his own 

 observations, that through Protolycosa of the Carboniferous period and 

 the existing Liphistius, Anthracomartus forms a direct transition to the 

 typical unsegmented Araneje, while he regards the interesting fossil 

 Kreischeria as a form very near akin to the existing Trogulidai. By 

 Haase (No. 17), however, the majority of Scudder's Anthracomarti are 



