76 PROC. ENT. SOC. WASH., VOL. 24, NO. 2, MAR., 1922 



tura is fully in accord with that drawn from other sources, 

 clearly indicating that the Protura are true insects. 



In many of the primitive representatives of the sub-class 

 Pterygota, the cardo "cp" of these insects is divided into 

 eucardo "ec" and paracardo "pc" as in Fig. 18, and the stipes 

 "bp" is divided into parastipes "ps" and eustipes "es" as in 

 Figs. 18 and 12. In a paper published in Vol. 23, p. 83, of 

 Psyche, in which these subdivisions were first described, I sug- 

 gested that the division of the cardo and stipes into two parts 

 might indicate traces of the union of parts formerly distinct. 

 I am now inclined, however, to regard the subdivision of the 

 cardo "cp" in Fig. 18, as of the same nature as the division of 

 the basal segment "cp" into two parts in the maxilla of the 

 crustacean shown in Fig. 25, in which the subdivision of the seg- 

 ment is purely secondary. Furthermore, the narrow marginal 

 sclerite "ps" of Figs. 18 and 12, may possibly represent the 

 narrow structure labeled "ps" in Fig. 25, but I have not been 

 able to obtain suitable material for definitely determining 



this point. 



Summary. 



The principal points brought out in the foregoing discussion 

 may be briefly summarized as follows: 



The Crustacea, rather than the chilopods or other "Myrio- 

 poda," furnish us with the prototypes of the various insectan 

 structures, and much of the misinterpretation of the parts in 

 insects is due to the fact that entomologists are largely ignorant 

 of the anatomy of the Crustacea. 



The basal segment of a crustacean buccal appendage forms 

 the cardo of an insect's maxilla. The second segment with its 

 endite in the Crustacea, forms the stipes with the lacinia in 

 insects. The third segment with its endite in Crustacea, forms 

 the palpifer with the galea in insects. The terminal segments 

 of the endopodite of the crustacean's buccal appendage forms 

 the palpus of an insect's maxilla. It is therefore incorrect to 

 state that the maxillary palpus of an insect represents the 

 exopodite of a biramous crustacean limb, while the galea and 

 lacinia represent the endopodite of such a biramous limb. 



Since the galea represents the endite of the third segment of 

 a mouthpart limb, and the lacinia represents the endite of a 

 second segment of such a mouthpart limb in insects, it is like- 

 wise incorrect to state that the mandible of an insect, which 

 corresponds to the basal segment alone of such a limb, may 

 exhibit structures corresponding to the galea, lacinia, and other 

 structures of the maxilla. 



The maxilla of an insect corresponds to the first maxilla of a 

 crustacean, and it is therefore incorrect to state that the "super- 

 linguae" of insects represent the first maxillae (maxillulae) of 



