ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 249 



only to a very limited extent ; recapitulation is confined to those portions 

 of the wing- in which there has been the least modification of the 

 primitive transversely banded type of marking. 



These bands, either in their primitive or modified shape, constitute 

 the ground colour. On this a second darker series of elements, the 

 markings proper, also usually transverse, are superimposed. The different 

 levels at which evolution in the pattern of the ground colour has halted — 

 that is, the configuration of the areas of ground colour — are the important 

 factors in determining the phylogenetic sequence of large groups. The 

 particular colours and markings determine the positions of the species 

 within these groups. 



These markings appear at the limits between ground colour and un- 

 pigmented areas, as one or more lines of dark scales along the edge of a 

 band adjacent to a white fascia or streak. The relative time of appear- 

 ance of the dark margin of any band in ontogeny is dependent upon the 

 time when the edge of that band became fixed in phylogeny. If late 

 racially, it will be late individually. This holds good irrespective of 

 whether or not there is recapitulation of phylogenetic changes in the 

 configuration of the colour areas during pupal development. Therefore, 

 in the second and more recent set of characters there is an actual 

 recapitulation. A dark markiug once permanently established in the 

 race tends to reappear independently of the ground colour, so that later 

 suffusion of the unpigmented area contiguous to it with ground colour, 

 or the shrinking away of the ground colour, does not affect its per- 

 manency. 



Later on in phylogenetic history additional dark markings, other 

 than those contiguous to unpigmented areas, may appear. The develop- 

 ment of these characters in the pupa becomes much abridged, and, 

 concomitant with this, their time of appearance is pushed back into the 

 earlier stages of pupal development, so that they may appear simultane- 

 ously with or even earlier than characters which are much older phylo- 

 genetically. However, only those characters permanently established 

 and of long standing in a species exhibit this precocity of development ; 

 recently acquired or variable characters appear in the order of their 

 phylogenetic sequence. When certain characters appear unduly early in 

 pupal development, physiological factors probably act directly in bring- 

 ing about this result. 



The most far-reaching and widespread changes have taken place 

 toward the place of the base of the wing, proximal to the transverse 

 vein. The final result is production of a uniform ground colour which 

 will be attained earliest near the base of the wing where evolution has 

 proceeded most rapidly. 



This observed evolution in the pattern of the ground colour suggests 

 that the uniform yellowish ground colour which suffuses the wing in the 

 higher Lepidoptera, beginning at the base and spreading distalward, is 

 the outcome of a phylogenetically older type of marking, originally 

 banded, and later fused to uniform colour, and the markings are a 

 second series superimposed upon the first. 



The observations made clearly point to the conclusion that the 

 evolution of the colour pattern in Lithocolletis has been orthogenetic. 



