Chap. XIV]. DEVELOPMENT AND EMBRYOLOGY. 239 



really been metamorphosed from true through eztremely 

 simple legs, is in part explained. 



Development and Embryology. 



This is one of the most important subjects in the 

 whole round of history. The metamorphoses of insects, 

 with which every one is familiar, are generally effected 

 abruptly by a few stages; but the transformations are 

 in reality numerous and gradual, though concealed. 

 A certain ephemerous insect (Chloeon) during its devel- 

 opment, moults, as shown by Sir J. Lubbock, above 

 twenty times, and each time undergoes a certain amount 

 of change; and in this case we see the act of metamor- 

 phosis performed in a primary and gradual manner. 

 Many insects, and especially certain crustaceans, show 

 us what wonderful changes of structure can be effected 

 during development. Such changes, however, reach 

 their acme in the so-called alternate generations of 

 some of the lower animals. It is, for instance, an as- 

 tonishing fact that a delicate branching coralline, stud- 

 ded with polypi and attached to a submarine rock, 

 should produce, first by budding and then by transverse 

 division, a host of huge floating Jelly-fishes; and that 

 these should produce eggs, from which are hatched swim- 

 ming animalcules, which attach themselves to rocks 

 and become developed into branching corallines; and so 

 on in an endless cycle. The belief in the essential iden- 

 tity, of the process of alternate generation and of ordi- 

 nary metamorphosis has been greatly strengthened by 

 Wagner's discovery of the larva or maggot of a fly, name- 

 ly the Cecidomyia, producing asexually other larvsB, 

 and these others, which finally are developed into ma- 



