Phyletic rurallilum in Metamorphic Species. 417 



The larva, of Vanessa Cm/ir/also, according to my 

 notes, are extremely constant in the first four 

 stages in spite of their complicated marking, but 

 become variable in the fifth stage, although to no 

 very great extent. 



I n Smerintkus Tilia, Ocellalus and Popuii also, 

 the greatest larval variability is shown only in the 

 last stage, the preceding stages being very con- 

 stant. These cases by no means depend upon 

 the marking of the young stages being simpler 

 and therefore being less capable of varying. The 

 reverse case also occurs. In a somewhat similar 

 manner as the young of the tapir and wild hog 

 are striped, while the adult animals are plainly 

 coloured, the young caterpillars of Saturnia 

 Yamamai possess longitudinal black lines on a 

 yellow ground, while as early as in the. second 

 stage a simple green colour appears in the place 

 of this complicated but perfectly constant marking. 

 If the young stages are so frequently constant, 

 this rather depends upon the fact that the trans- 

 ference of a new character to these stages not 

 only takes place gradually, but also with continually 

 diminishing energy, in a manner somewhat similar 

 to physical motion, which continually diminishes 

 in speed by the action of resistance till it is com- 

 pletely arrested. This constancy of the younger 

 stages may further be due to the circumstance 

 that the characters would only be transferred when 

 they had become fixed in the last stage, and were 



E e 



