38 Psyche [February 



represents the line of development of the higher Crustacea (Iso- 

 pods, etc.), while "B" represents the hne of development of the 

 lower Insecta, and "C" represents the line of development of the 

 ''^Nlyriopoda", all of which were derived from a common ancestral 

 group "D", some of whose members contained the factor or group 

 of factors "x", which produces a flat head with mandibles ex- 

 tending up the sides of the head to a point behind the eyes (as 

 the insect Lepisma, and the isopod Asellus) while others of the 

 ancestral group contained the factor "y," which produces a 

 pyriform head with cryptognathous (endognathous} mouthparts 

 (as in the insect Campodea and the "myriopod" ScoIopendreUa). 

 It should be quite evident from the diagram in Text figure 2 

 that certain insects in "B" could inherit the characters "x" 

 (flat head with huge mandibles) from the "side" of, or in common 

 with, certain higher Crustacea in "A", having inherited these 

 tendencies or factors from the common group "D", which gave 

 rise to both "A" and "B", while certain other insects in "B" could 

 inherit the characters "y" (pjTiform head with cryptognathous 

 mouthparts) from the "side" of, or in common with certain 

 Symphyla ("myriopods") in "C", having inherited these tend- 

 encies from the common ancestral group "D", which gave rise to 

 both "B" and "C", without postulating that members of "A" 

 and "C" must have interbred to produce these characters in "B". 

 In order to apply the same principle to the orders of insects, let 

 us suppose that "A" represents the line of development of the 

 Psocids, "B" that of the Hymenoptera, and "C" that of the 

 Coleoptera, all of which were descended from ancestors resembling 

 the Protorthoptera in many respects, which may be represented 

 by the ancestral group "D". If "x" represents the factor or 

 factors producing colonial tendencies, while "y" represents the 

 factors producing styli-bearing ovipositors, for example, it should 

 be readil}^ apparent from the diagram, that some members of both 

 Psocids ("A") and Hymenoptera ("B") could inherit tendencies 

 toward "social" life (represented by "x") from a common source 

 in "D", while some members of both Hjmienoptera ("B") and 

 Coleoptera ("C") could inherit their tendencies toward the 

 development of styli-bearing ovipostors (represented by "y") 



