82 



EVOLUTION IN COLOR-PATTERN OF THE LADY-BEETLES. 



there, in one direction or the reverse direction. In fig. 90 the variations 

 of Hippodamia convergens are arranged to show this. In fig. 11 they were 

 arranged merely to show the successive steps of the several lines of devel- 

 opment. There is no kinetic or progressive principle here at work causing 

 a general march. Rather, these beetles have a repertoire of development- 

 lines which are called into activity here and there as the environment sets 

 one or another into play. This repertoire variation is illustrated in table 20. 

 The one variation that has appeared most frequently is spotlessness. I 

 believe that this is because loss as such is an exigency to which determin- 

 ers in the germ-plasm are more subject in the long run than any other; 

 just as all kinds of machinery have this one frequent cause of disablement 

 in common, the loss of some part. This item in the repertoire of varia- 

 tions is, then, common to most characteristics and organisms. When an 

 organ is composed of many cooperating parts, such as an eye, this liability 

 to loss or deficiency of one or another feature of its make-up renders it 

 more liable to variations of defect than a characteristic which is simple in 



TABLE 20. Repertoire variation in the color-pattern of the Coccinellidaz. 



[For key to table sec page 83.] 



