12 Mr. R. I. Pocock on the 



rare exceptions, there are eight eyes arranged 



in median and lateral groups Caulogastra. 



Order 2. Pedipalpi. 

 3. Arane^. 

 B. Cephalothorax and abdomen not separated by a 

 deep constriction ; the first abdominal sternite 

 not acting as an operculum to the anterior 

 abdominal respiratory stigmata. Breathing- 

 organs in the form of tubular tracheal. Usually 

 a single pair of eyes, rarely two pairs. 



a. A pair of respiratory stigmata between the 



fourth and fifth cephalothoracic appendages. 

 The posterior two cephalothoracic somites 

 not covered by the cephalic shield. The 

 posterior legs with a series of racquet-shaped 

 tactile organs on the two basal segments ; 

 the trochanter of the two posterior pairs 



of appendages bisegmented, &c Mycetophora. 



Order 4. Solifug^. 



b. No stigmata between the coxse of the fourth 



and fifth appendages. The cephalothorax 

 covered by a continuous shield. The pos- 

 terior legs without racquet-shaped tactile 

 organs, and the trochanters of all the legs 



undivided &c Holosomata. 



Order 5. Pseudoscobpiones, 



6. Opiliones. 



7. ACARI. 



This classification differs considerably from that proposed by 

 Prof. Lankester in his article ^'Limulus an Avachnid^^ already 

 mentioned. This autlior united the Scorpiones, Pedipalpi, 

 and Aranea^ in a group termed Aerobranchia, while the Soli- 

 fugse, Pseudoscorpiones, Opiliones, and Acari constituted a 

 corresponding group, Lipobranchia. This terminology, how- 

 ever, does not allow for the fact tliat nearly all the higher 

 Araneffi are partially or wholly Lipobranchiate. 



Moreover, although the Opiliones, Pseudoscorpiones, and 

 Acari were placed in the same section of the Class, it appears 

 from the genealogical tree published in the paper referred to 

 above that these three orders have had an independent origin, 

 the Acari being an offshoot from the stem of the Araneas, the 

 Pseudoscorpiones from that of the Scorpiones, and the Opi- 

 liones from the Solifugge. If this be so, it is not easy to see 

 upon what grounds the Lipobranchia can be considered a 

 natural group. 



As for Dr. ThorelPs genealogical tree, enough has already 



been said to show how mateiially this author's opinions differ 



from my own. It may be added, however, that the Solifugse 



are removed from the Arachnid phylum and attached to that 



of the Hexapoda and Myriopoda, a view which to me is quite 



unintelligible. 



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