PACKARD. — INHERITANCE OF ACQUIRED CHARACTERS. 359 



the forms are evidently the result of adaptation in response to a series 

 of stimuli whose nature is in part appreciable but in part unknown. 



It may be noted, however, that the appearance of a primitive band 

 in the second larval stage indicates tbe origin of these forms, as well 

 as that of insects in general, from a Peripatus-like, and again from an 

 earlier leach-like Annelid ancestor. Hence the first larval or Cyclops 

 sta^e is due to a precocious development caused by the unusual 

 environment, and is simply adaptational, and not of phylogenetic 

 significance. 



*&* 



V. Ox the Inheritance of Acquired Characters in 



Lepidoptera. 



Perhaps in no other group of animals may we study the subject of 

 the inheritance of acquired characters with more success than in the 

 Lepidoptera. In these insects the four stages of existence, the egg, 

 larva, pupa, and imago, are definite and fixed, and during each of the 

 last three the organism is, so to speak, a differeut creature, with dis- 

 tinct and separate shape and structure external and internal, and during 

 each stage leads a different life. Family, generic, and specific charac- 

 ters are inherited at each of these stages, and at each there is a com- 

 bination of congenital and acquired characteristics, some. of both classes 

 of which, i. e. the least marked, are difficult to separate from one 

 another. The following is an attempt at a rough grouping of such 

 features at the last three stages. 



We omit the egg stage, for though they more or less vary in shape 

 and ornamentation, this is perhaps due more to difference in the struc- 

 ture of the lining of the oviduct of the female than to the action of 

 external circumstances on the egg after it has been laid. Yet this 

 should be said with some reservation, because we are not aware that 

 any one has discussed the probable mode of origin of the specific dif- 

 ferences in the shape and color of the eggs of birds, or the shape and 

 markings of the eggs of insects ; though undoubtedly the agency of 

 external causes together with natural selection has something to do 

 with the variation.* 



* It has seemed to us that the relation of specific and generic characteristics 

 in the eggs of insects is a most difficult problem. Yet it should be observed 

 that, while the differences in ornamentation and shape are primarily due to the 

 impression on the shell received from the lining of the oviduct, yet the wonder- 

 ful diversity we see in the eggs of insects is often readily seen to be correlated 

 with the external conditions in which they exist, after having been deposited 

 by the parent. As regards the eggs of birds, the thick solid shell and conico 



