178 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Relationships between Classes of Arthropoda.* — G. H. Carpenter 

 contributes a valuable essay on this difficult siibject, and comes to the 

 following principal conclusions : — 



(1) The Arthropoda are a natural, monophyletic assemblage of 

 animals. 



(2) There is exact numerical correspondence between the segmenta- 

 tion of typical Insects, Crustaceans, and Arachnids (worked out in a 

 detailed comparative table). 



(3) Such correspondence in three distinct classes cannot reasonably 

 be explained as the result of convergent evolution from ancestors with 

 very numerous segments, which independently became diminished to 

 exactly the same extent. 



(4) The ancestral Arthropods must, therefore, have possessed a fixed 

 and definite segmentation ; and the various forms with very numerous 

 segments (Phyllopods, Millipedes, etc.) have undergone abnormal 

 elongation. 



(5) The Insecta, Chilopoda and Diplopoda may be derived from 

 common Symphylan ancestors, which branched off from the primitive 

 Crustacea (proto-Leptostraca) . 



(G) 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. A genealogical 

 tree is given expressing these conclusions in graphic form. 



o. Insecta. 



Economic Entomology .f — F. V. Theobald discusses a great variety of 

 subjects in his first report on economic zoology, but the majority are 

 entomological. They afford a fine illustration of the multitudinous- 

 ways in which man comes into practical contact with animal life, and 

 the author deserves congratulation on the impressiveness of his " First 

 Report." There are discussions on cereal pests, root-crop pests, fruit 

 pests, garden pests ; on dipterous larvse in human excreta ; on Anobium 

 tesselatum in St. Albans Cathedral ; on the cigar beetle ; on the tsetse 

 fly ; on locusts in the Sudan ; and on mosquitos at Blackheath, and 

 so on. And inter alia we find information on poison for moles ; tape- 

 worm in sheep ; the origin and varieties of domesticated geese ; green 

 matter in Lewes public baths ; the screw-worm in St. Lucia ; the Teredo ; 

 the Ceylon pearl fisheries, and so on, through a variety of subjects as 

 interesting as it is astounding. 



* Proc. K. Irish Acad., xxiv. (190::) pp. :;20-60(l pl.\ 



t First Keport ou Economic Zoology. British Museum. 1D03, xxxiv. and 192 pp., 

 18 fies. 



