in McUun,-f>liic Species. 419 



affects only the first stage, while the second has 

 just commenced to affect the fifth stage. Such a 

 supposition is not opposed to any theoretical con- 

 siderations, but rather has much probability in its 

 favour, since we know that species are from time 

 to time subject to be remodelled ; and further, 

 that the coalescence of several stages of phyletic 

 development in the ontogeny of one and the same 

 species (see p. 226, development of the genus 

 Deilephila) shows that during the backward 

 transference of one character, new characters may 

 appear in the last stage of the ontogeny, and in- 

 deed very frequently at a time when the next 

 youngest character has not been transferred back 

 so far as to the first stage. 



That this secondary variability is to a certain 

 extent brought about by the conflict between the 

 old and new characters, the latter striving to sup- 

 press the former, is shown by the caterpillar of 

 Saturnia Carpini which I have observed for 

 many years from this point of view, and than 

 which I do not know a more beautiful illustration. 



When these larvae leave the egg they are black, 

 but in the adult state are almost bright green 

 this at least being the case in a local form 

 which, from the district in the vicinity of Genoa 

 where it is found, I will designate as the var. 

 Ligurica. Now whilst these two extreme stages 

 of development are relatively constant, the inter- 

 mediate stages show a variability which becomes 



E e 2 



