40 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.30. 



descendants of the centipedes. The myriopodists find that the differ- 

 ent forms of the Cliilopoda may be arranged in a series indicating a 

 progressive reduction and disappearance of alternating segments. If 

 this process should be continued far enough and accompanied by the 

 disappearance of most of the legs, together with a few other changes, 

 there would undoubtedly be produced an insect-like creature. Or, 

 again, the same result might be obtained if the reduction in the number 

 of segments were brought about by a combination of the cbilopod 

 segments instead of by an obliteration of the supernumerary ones. 

 Hence, the evolution of insects from centipedes may be explained in 

 two ways, but it would seem that the myriopodists simply assume the 

 fact of this evolution which they would so amply explain. While 

 probably few entomologists disclaim a common origin for the Cliilo- 

 poda and Hexapoda, yet probably few of them admit that a study of 

 insects alone affords any evidence of a lineal descent of the latter from 

 centipedes. While it may be true, then, that the myriopods appear 

 to be evolving into insects, it is not true that insects appear to have 

 descended lineally from centipedes. The alleged relationship seems 

 to be a case of a myriopodan claimant. 



The theory that an insect is a centipede which has lost most of its 

 segments by reduction has been elaborated chiefly by Verhoeff, but 

 that author's ideas have been so widely criticised, especially by 

 European entomologists, that the writer will not reiterate the subject 

 here.*^ The bulk of opinion favors the notion that the intersegmental 

 plates are secondary sclerites cut off from the front parts of the 

 thoracic segments. Cramp ton (1909) has given the general term of 

 intersegmentalia to all the sclerites that occur between any two seg- 

 ments, while Enderlein (1907) designated the special group appar- 

 ently derived from the front of any segment as the apotom of that 



a The writer has heretofore overlooked the theory of Hagen (1889) that each thoracic 

 Begment of modern insects is a composite of three primitive segments, the first of which 

 carried the wings, the second the legs, and the third the spiracle. Hagen's reasoning 

 is a good example of the exasperating style of logic such writers always use for closing 

 their argument at both ends. For example, after stating his proposition, he expects 

 the reader to accept its truth simply because it explains the structure of the thorax 

 BO nicely, as if this in itself were sufficient evidence. In the first place, the author 

 assumes that there is something to explain, and, in the second place, he gives no 

 reason why the parts have not been produced secondarily from one primitive segment, 

 as they so evidently appear to be formed to students of development. The negative 

 argument, that embryos of insects do not indicate any such thoracic composition, is 

 set aside, after the manner of all such writers, by the statement that the condensation 

 of the three segments into one took place so far back in phylogenetic history that even 

 the embryo shows no longer any trace of it. ("Ich miene also, dass diese Cumulation 

 von je drei Segmenten einen so alt erworbenen Zustand darstelle, dass selbst im 

 Embryo der Nachweiss nicht mehr vorhanden ist. ") This argument must give a 

 feeling of profound peace to all who seek its blissful security. Who enters here leaves 

 all doubt behind and shuts out all pursuit. In this garden of Eden anybody can 

 Lave all creatines created according to hie own private formulas. 



