30 PROCEEDINGS OF THE ACADEMY OF [Jan., 



ternal complex, the antecoxal laterale, the furci-sternum (described 

 later), and the katepimeron form a closed ring about the base of the 

 leg, and might consequently be taken for a portion of the leg region; 

 but, for the reasons above stated, this view would be extremely 

 improbable. 



Hansen, '93, compares the trochantin to the coxopodite of the Mala- 

 costraca, and homologizes the coxa with the basipodite. He likewise 

 adopts the views of Wood-Mason, '79, and Jourdain, '88, who pro- 

 pose that the styli on the meso- and meta-thoracic coxae represent the 

 exopodite of the crustacean leg. In a recent article Bonier has again 

 brought this theory into prominence. Henneguy, '04, who likewise 

 compares the insect leg with that of the Crustacea, differs from the 

 above-mentioned investigators in that he maintains that the stylus 

 corresponds to the epipodite — not to the exopodite. He argues that 

 if the coxa corresponds to the basipodite, the stylus or coxal appendage 

 must correspond to the epipodite or basipodite appendage, and not 

 to the exopodite, which is the appendage of the coxopodite. 



The above-mentioned views seem hardly probable, for all indica- 

 tions point to the fact that insects are not descended from aquatic, 

 but from terrestrial ancestors. Palmen, '77, has demonstrated that 

 the open tracheal system for aerial respiration is the primitive one, 

 and it may be added that in the development of the Ephemerid embryo, 

 the primordia (or fundaments) of the spiracles may be observed even 

 in the germinal streak. The aquatic life of the larva?, then, must be 

 regarded as a secondary adaptation; and, therefore, one can hardly 

 attempt to homologize the styli of the insect leg with the exopodite 

 or the epipodite of the aquatic Crustacea. 



Banks', '93, theory that the styli are vestigial legs has no founda- 

 tion other than the extremely improbable supposition that each seg- 

 ment is double. In all probability these structures are modified sen- 

 sory hairs, or they may be comparable to the movable spine-like struc- 

 tures found upon the legs of certain insects. Verhoeff, who adopts 

 Haase's, '89, view regarding the styli, homologizes them with the 

 coxal organs of the Myriopoda. 



As has been stated, Walton, '00, believes that the meron is a vestigial 

 leg, but serious doubt is cast upon this theory by the fact that one can 

 trace the formation of the meron as a coxal sclerite, which is either 

 not distinguishable from the rest of the coxa, or at most indistinctly 

 traceable, in the lower forms, but becomes detached by muscular ten- 

 sion in the highly specialized insects. The view that the tension of 

 the muscles attached to it causes the meron to become detached is 



