PACKARD. INHERITANCE OF ACQUIRED CHARACTERS. 363 



steps in the evolution of the adaptational characters which appear 

 after the first exuviation. It seems very probable that these later 

 features were the result of the action of external stimuli, both physi- 

 cal and biological, and that they were acquired not only during the 

 lifetime of the larva, but at certain distinct stages or periods during 

 the growth of the creature. The changes are both colorational and 

 structural, aud during the different stages the larva was adapted for 

 different surroundings, and thus at each important stage was virtually 

 for the time being a distinct animal. 



During the pupa stage special aud unusual structural adaptations 

 arose ; the cremaster being unusually developed, and also a pair of 

 cephalic hooks, serving to entangle the head in the web of the cocoon, 

 so that the pupa cannot be thrown out of the curled leaf which remains 

 in the fir.-t brood on the tree. These I regard as characters acquired 

 by the insect after birth, and in response to the exigencies of life at 

 different stages. The reader is also referred to the conclusions given 

 in that paper. 



Acquired Characters in the Notodontidoe. — In the systematic por- 

 tion of my work on this group I have given a number of life histories 

 of the family from papers recently published, and with more or less 

 detail pointed out the later adaptational, as distinguished from the 

 congenital characters. I have called attention, in late articles, to 

 the varying shape of the tubercles and setre in the larvre of the Bom- 

 byces and other of the higher Lepidoptera, and to their probable mode 

 of origin, and why they appear on certain segments in preference to 

 others. The attention of the reader is called to the summary or re- 

 capitulation of changes especially in the life history of Datana inte- 

 gerrima, Ajuitelodes torrefacla, Symmerista albifrons, Macrurocampa 

 marthesia, and several species of Centra, while there is a summary of 

 the steps in the assumption of the adaptive characters at the different 

 larval stages of Schizura. The steps in the evolution of what may 

 be regarded as acquired characters in Schizura. and in Dasylophia 

 anguina, Hyparpax, Heterocampa, etc., are readily seen by an exami- 

 nation of the plates in the monograph referred to. 



The Notodontians are remarkable in general for the humps, tuber- 

 cles, and spines of their larvae, some of which are congenital, while 

 others appear at different stages after birth. Still some larva; of this 

 group are entirely without them, and remain so throughout their 

 larval life. And this is an argument that the various processes of the 

 cuticle or outgrowths of the entire integument are characters origi- 

 nally acquired during the post-embryonic life of the young insect. 



