Abstract From a critical reading of S. M. Manton's “The Arthropoda” (1977) and D.T. Anderson's “Embryology and phylogeny in Annelids and Arthropods” (1973) it is shown that the “functional morphology” of these authors used in phylogenetical sense is old fashioned “Lamarckism” and thus unsuited for phylogenetical considerations. A comparison of Mayr-Simpson's evolutionary systematics and Hennig's phylogenetical (cladistical) systematics is to the advantage of the latter. It is concluded that a final decision on the phylogeny of Apterygota—as on any other phylogeny—must be based on an evaluation of the plesiomorphous or the apomorphous state of the characters.