HARDWICKE'S SC lEN CE-GOS SIP. 



109 



embryo of the larva within the egg, to the ultimate 

 formation of the pupa-skiu by their agency. 



We may summarize these wonderful changes in 

 this way. A number of parts become doubled in 

 the embryo, as far as their integument or skin is 

 concerned, so that they have an inner skin and an 

 outer one. The inner skin becomes detached and 

 remains as an organ of reserve for the formation 

 of the pupa. The outer one undergoes immediate 

 development, and forms the exterior of the larval 

 the inner one awaiting its proper time to take up 

 the developmental history from the early embryonic 

 period after the outer one has played out its part. 

 The larval period is, as it were, a period grafted in 



Tig. 79. The mouth of the Gadfly ( TulmnKn) , seen from above, 

 rn, inentum; /, Jignia; ;;, maxillary palpi; ?/(</, the principal 

 lancets. 



between the embryo and the imago, without affect- 

 ing the development of the latter to any material 

 degree. Strange as such a phenomenon may appear, 

 it is by no means confined to insects; something of 

 the same kind occurs frequently amongst star-fishes 

 and other echinoderms, in many worms, as well as in 

 some few crustaceans. 



Without attempting to trace the complex phe- 

 nomena attending this mode of development, enough 

 has been done to show the extreme difficulty which 

 occurs in determining the exact nature of the 

 various organs in the butterfly's mouth. 



Most authors have hitherto agreed in describing the 

 antlia,or spiral sucking organ, as a modification of the 

 great maxillae of other insects, and the large-jointed 

 palpi, p, as labial palpi. A more careful examina- 



tion of the developmental history, and of the rela- 

 tions of these organs with the other parts of the 

 mouth, shows clearly, however, that this is not the 

 case. The antlia are undoubtedly a modification of 

 the second pair of maxillaj — indeed they are iden- 

 tical with the paraglossa) of the bee, — whilst a com- 

 parison with the mouth-organs of the fly shows 

 clearly that the so-called labial palpi are really 

 maxillary palpi, a view which is borne out by their 

 anatomical relations. The critical examination of 

 this question is one of extreme difficulty, and would, 

 therefore, be out of place in Science-Gossip. 



Fig. so. The extremity of the principal lancets of the Gadfly. 



The adaptation of the nectaries of flowers, and of 

 their reproductive organs, to the antlia of lepido- 

 ptera, is one of the most remarkable and beautiful 

 of Nature's works. Every tyro knows how de- 



Fi^-. SI. The proboscis of the common House-fly, with the 

 labrum dislocated from its groove. 



structive the ravages of lepidopterous larvae are, 

 and yet we must probably thank the perfect insects 

 for the great glories of the floral world; for, as 

 Charles Darwin has pointed out, it is only amongst 

 plants which require, or are greatly benefited by 

 insect agency, in the process of fertilization, that 



