Phyhgeny of the Arachnida. 303 



and that of the Insects, compels me to think that the rchi- 

 tinnshij) hctwcen Arachnids and Crustaceans is a hjj)othesis 

 whicli will be untenable in future ; " and considering further 

 the fact that the most important observations on the develop- 

 ment of Limulus and the Arachnids and on the structure of 

 the latter — observations which von Kennel does not touch 

 upon at all — were not published until after the apj)earance of 

 Zofjraff's paper, it is natural that in his last ])aper the scientist 

 in question should wish to discuss the relations between the 

 Arachnida and the rest of the Tracheata. 



Like von Kennel, Lang also {loc. cit. pp. 560-562) finds it 

 necessary to assume that the Tracheates divided at an early 

 period into two independent branches ; yet in so doing he 

 proceeds not from the position of the genital aperture, a 

 character to which apparently he attaches no great signifi- 

 cance, but rather from the comparison of the first three or 

 four pairs of appendages : consequently, in opposition to von 

 Kennel, he contrasts the Arachnids with all the rest (Cheli- 

 cerata and Antennata). The main reason for uniting the 

 Arachnoids with the Tracheates, and for separating them from 

 the Xiphosura and Gigantostraca, is the same in this case 

 also, namely the presence of the Malpighian tubes and trache;^ 

 in the Arachnoids and their absence in the Xiphosura. The 

 homology of the Malpighian tubes in all Tracheata is placed 

 by the author beyond all doubt, but in his opinion the assump- 

 tion of an independent appearance of the tubular trachene 

 " could only be admitted as a makeshift." Lang considers 

 that the Scorj)ion must undoubtedly be regarded as the type 

 nearest allied to the ancestral forms of the Arachnids, while 

 with regard to the Solifugae he holds such a hypothesis to be 

 probable, though still in need of confirmation [loc. cit. p. 558) ; 

 hence lie does not exj)lain why it is that the Scorpion, which 

 has retained the largest number of stigmata and primitive 

 conditions generally in the segmentation of its body and in 

 its organisation, possesses the most modified trachete, and 

 why in the forms that exhibit the greatest divergence in 

 organization, it is precisely the tracheaj that are less modified 

 (regarding the fascicular trachea as the most primitive type) 

 than in the Scorpion and the Solifugffi. This discrepancy, 

 neglected by Lang, has been perceived by Schirnkewitsch. 

 The latter regards tiie Scorpion as a more primitive form 

 tlian tlie Spiders, which, however, he considers to be less 

 modified than the Opilionidaj and the Acarina, while he 

 believes that the original respiratory organs of the Arachnids 

 were lungs, though these were developed from unbranched 

 fascicular trachcai (No. 57, p. 67). 



21* 



