Carpenxeu — lieiationskipti between Claancn of Arthropoda. 353 



5. The Insecta, CMlopoda, and Diplopoda may bo derived from 



common Symphylan ancestors, which branched off from 

 the primitive Crustacea (proto-Leptostraca). 



6. Among the Crustacea, the Leptostraca and the Trilobita show 



the most primitive characters. The proto-Trilobita had 

 the typical Arthropodan number of segments. 



7. The Arachnida, including the Merostomata, Xiphosura, and 



Pycnogonida, arose from the proto-Trilobita. 



8. The Malacopoda must be regarded as Arthropoda of low type. 



They have no close relationship to Chilopoda or Insecta, 

 and their Annelidan affinities are doubtful. 



9. The Arthropoda, as a whole, probably sprang from Naupliform 



ancestors, and not from well-developed Annelid- worms. 



The genealogical "tree" (Plate VI.) may serve to show these 

 conclusions in a graphic form. 



[Table. 



