ANCESTR Y AND CLASSIFICA TION. 239 



characters now common to the group, or which 

 exist under some modified form in this or that 

 offshoot, such special peculiarities being subse- 

 quent, more individualized developments of the 

 ancestral type. 



With this clue, a careful study of the structure 

 of each stage will give a result not far removed 

 from the following. 



The egg was globular, with flattened base, its 

 surface nearly smooth, but covered with faint re- 

 ticulations, growing more minute next the micro- 

 pyle, which formed a series of five to seven kite- 

 shaped cells arranged symmetrically around a 

 common centre. 



The caterpillar had a large, smooth, rounded 

 head, a body composed of thirteen segments, 

 nearly uniform in size, the first bearing above a 

 chitinous shield, the first three a pair of horny 

 legs, the sixth to the ninth and the last segments 

 a pair of fleshy legs, spiracles upon all the seg- 

 ments except the last two, but those of the second 

 and third in a very rudimentary condition, so as 

 to be physiologically useless. The surface of the 

 body was covered profusely with little papillae, 

 from each of which sprung a minute simple hair. 

 The new-born caterpillar, however, differed per- 

 haps in this respect from the full-grown, in that 

 its body was furnished with short club-shaped 

 hairs arranged in dorsal, pleuro -dorsal, and sub- 



