THE 



AMERICAN JOURNAL OF SCIENCE 



[FO URTH SERIES.] 



Art. XXXVIII. — The Ancestry of Insects with particu- 

 lar references to Chilopods and Trildbites / by John D. 



TOTHILL.* 



Introduction. 



Dating practically from the publication of Darwin's " Ori- 

 gin of Species," a fund of energy has been directed toward 

 elucidating the probable descent of the various groups of liv- 

 ing organisms. In these various groups different hypotheses 

 of derivation have sometimes followed one another in rapid 

 succession. Each in its turn has been of value as a working 

 hypothesis and has often served to elicit new facts that have 

 formed the basis of a supplanting hypothesis. 



In the case of the Hexapoda the usual gamut of systems of 

 classification and of genealogy — the one a necessary hand- 

 maiden of the other — has been proposed. We owe to the 

 Greek civilization in general and to Aristotle in particular the 

 first attempt to arrange insects in a system of related groups. 

 In the interim between this first attempt (about 300 B. C.) 

 and the more recent one of Handlirsch (1908) there have been 

 many derivations proposed. Of these it is necessary simply to 

 mention one or two of the more interesting. In 1866 Haeckel 

 proposed a genealogical tree deriving the Insecta through the 

 "Tocoptera" which included the "Thysanura," from " Tra- 

 cheata" which also gave rise to the Arachnids and Myriopods. 

 Three years later Brauer suggested a derivation through the 

 Apterygogenea or wingless insects including Campodea and 

 Thysanura; Brauer's system of classification was based on 

 morphology, metamorphosis, and later on embryology ; it was 

 thorough -going and forms the basis of all subsequent systems; 



* Contribution from the Buseey Institution No. 119. 



Am. Jour. Sci. — Fourth Series, Vol. XLII, No. 251. — November, 1916. 

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