me:\i()ii;s of tiik national academy of sciences. 39 



wise moditied or spociiilizcd, und comertod into an enormously lono- instrument for probing the 

 deep tubular corollas of orchids. 



The palpi of Sphin_o-id;e are always three-jointed an<l rather larye, while those of the Cerato- 

 campinte have lost the third joint, but in the Agliina^ and Huna-iniv^ they are large and often 

 three-jointed. 



The legs of Sphingida^ are stouter and provided with stout spines, thus diU'ering from those 

 of the Ceratocampida% which are comparatively weak and unarmed. 



The genitals of Sphingidse are in certain genera like those of Ceratocampids\? and do not 

 present family' distinctions. 



We have seen that there is in reality but a slight break or gap between the Ceratocampidaj 

 and Sphingida". Were it not for the changed positions in the lar\a of tubercle r, the presence 

 of an additional branch of the radius vein strengthening the costal edge of the fore wing, and 

 of the frenulum, there would be no absolute characters separating the primitive Sphingidfe 

 (Smerinthina:'. especiallj^ Cressonia) from the Cei-atocauipidfe. The lai-ger head, fusiform or 

 prismatic antenuiv, long maxilla?, narrow, strong wings, stout, spiny legs, and the slight difler- 

 ences in the larva and pupa are simply adaptive characters, due to exercise of the modified organs, 

 the result of the greater activitj- of the imago in seeking its food, in probing the deep corollas 

 of flowers, and in seeking their mates. 



The revival, restoration, or reacquisition of j/artially atrophied organx. — We have observed 

 what a great range in size and adaptability for probing tul)ular corollas is seen in the develop- 

 ment of the raaxillffi of the Sphingid;?, from an almost rudimentarj' condition in Cressonia to 

 those of the common potato Sphinx (Phlegethontius), and to the enormously long one of the 

 South American Sphinx, and that this is evidently the result of use, and of use-inheritance. 

 This is correlated with the nari'ow, powerful wings, the large thorax due to the enlarged muscles 

 which raise and lower the wings; with the stout spin}' legs, and the large head. 



If, as we have attempted to show, by presenting the facts supporting the view that the 

 family of Sphingidfe has directly descended from some member of a detinite family, i. e.. the 

 Ceratocampidie, then we have to deal with instances of a most remarkable phenomenon, that of 

 the revival, restoration, or bringing back to active use, and consequent increased development, 

 of organs or structures which in the ancestral or stem forms have become partially or almost 

 wholly' atrophied from disuse. It is universally the case that an organ, once wholly atrophied, 

 never becomes restored or revived so as to function or be of any service in the animal economy. 

 We have seen that in the case of the wings, a branch of the radius vein (III) either entirely' 

 atrophied or only vestigial in dift'erent groups of Saturnoidea becomes greatly developed in the 

 Sphingidis, thus strengthening the costal edge of the wing. This is a clear case of the restoration 

 or reacquisition bj' exercise of a structure or organ. 



Another case is that of the maxillte. We should regard those of Cressonia as rudimentary 

 rather than vestigial; but those of the Saturnoidea are, as anyone will acknowledge, vestiges of 

 organs which, in the ancestors of the group, were well developed and of constant use to the 

 insect, as in the Noctuidse. It follows from this that here we have an instance, and we know of 

 none others on record, of the complete revival or restoration of the muscular, nervous, and 

 mechanical power and activity of a lapsed or nearly atrophied organ. 



The infinite variety in the morphology of tiie inouth-parts of the arthropod phyla does not 

 afi'ord, so far as we are aware, such an instance. It is a nearly universal law that an organ in 

 the last stages of atrophy is never restoi-ed to its pristine structural and functional activitj'. 



To suppose that by any process in nature the lost digits of a horse could ever be restored, 

 and that the splint bones could in the descendants of the modern horse in future ages be restored 

 and function as usable toes, seems on the face of it an absurdity; and yet in the useless tongue of 

 the ceratocampid moths we have, unless we are mistaken, an organ which, in the descendants of 

 the group, has become restored in form, structure, and vigor, and so greatly enhanced in develop- 

 ment as to form a most striking case of restoration by simple exercise maintained through many 

 o-enerations. 



