38 
Psyche 
[February 
represents the line of development of the higher Crustacea (Iso- 
pods, etc.), while “B” represents the line of development of the 
lower Insecta, and “C” represents the line of development of the 
“Myriopoda”, 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 isopocl 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” Scolopendrella) . 
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” (pyriform 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 readily 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 Hymenoptera (“B”) and 
Coleoptera (“C”) could inherit their tendencies toward the 
development of styli-bearing ovipostors (represented by “y”) 
