268 Journal New York Entomological Society, t^'oi- xxiv. 



In the development of recent Arthropoda, the lines of descent 

 which have the most closely paralleled the line of descent of the 

 Insecta, are those of the Crustacea, Diplopoda, Chilopoda and Sym- 

 phyla (see fig. 2). Indeed, the Crustacea, " Myriopoda " ( i. e., Chi- 

 lopoda, Diplopoda, and Symphyla) and Insecta, may be regarded as 

 forming the three apices of a triangle, each of whose apices is con- 

 nected with the other two by mutual bonds of relationship. Among 

 the Crustacea, the Arthrostraca {c. g., Anaspides, Koonnnga, Bathy- 

 nella, etc.) and have retained certain characters suggestive of the 

 ancestral condition of insects, but, on the whole, the " Myriopoda " 

 {sensu lata) and Scolopcndrella in particular, are more closely related 

 to the Insecta than any other Arthropods. 



The parts of the head, legs, and abdominal appendages of the 

 Apterygotan insects are strikingly like the corresponding parts of the 

 " Myriopoda," and even with regard to their embryological details, 

 the Apterygota are very like " Myriopods," as has been pointed out 

 by Philiptschenko, 1912, Lignau, 1911, Heymons, and others. 

 Furthermore, the points wherein the Apterygota differ most from 

 higher insects, are those wherein they approach more closely to the 

 " Myriopoda " and Crustacea, and from the standpoint of compara- 

 tive anatomy and embryology, there can be no doubt that the Aptery- 

 gotan insects are the most primitive — and have therefore departed 

 the least from the probable ancestral condition of insects in general. 



Despite the fact that the paleontological record is confessedly in- 

 complete, and notwithstanding the fact that such extremely fragile 

 and rare insects (for they have apparently never been very numer- 

 ous) could not be expected to leave many traces in the lower strata, 

 which have been subjected to great pressure and upheaval, Hand- 

 lirsch and his followers would use the lack of Apterygotan remains in 

 the earlier strata as an argument against the view that the Aptery- 

 gota should be regarded as the nearest living representatives of the 

 ancestors of the Pterygotan forms. In their efforts to widen the 

 gap between the Apterygota and Pteryigota, these authors would even 

 go so far as to remove the Apterygota from the class Insecta (or 

 Hexapoda) and would place them in a distinct class, or classes by 

 themselves ! The fact remains, however, that from a morphological 

 point of view (and aside from the presence or absence of wings) 

 there is an infinitely wider gap between the Blattid?e and Chalcididse — 



