46 KANSAS UNIVEKSITV (J'JARTERLV. 



following course: First, the variations in form of this organ should 

 be observed, including palaeontological evidence if possible; then its 

 function or functions should be determined. With this knowledge 

 endeavor to determine what was the primitive form of the organ and 

 the various ways in which this primitive form has been modified, 

 keeping in mind the relation of change in form of the organ to its 

 function. In other words to read the action of natural selection upon 

 the group of organisms as it is recorded in a single organ. The data 

 thus obtained will aid in making a provisional classification of the 

 group. 



"When this stage has been reached another organ should be 

 selected and its history worked out in a similar way. 



"The results of the two investigations should then be compared; 

 and where they differ there is indicated the need of renewed study. 

 For hf rightly understood the different records of the action of natu- 

 ral selection will not contradict each other. The investigation 

 should be continued by the study of other organs and a correlating 

 of the results obtained until a consistent history of the group has 

 been worked out." 



In the study of the scales of the Lepidoptera, a study suggested to 

 me by Professor Comstock, I have endeavored to follow the lines 

 indicated in the above-described method, believing that systematic 

 workers who accept the theory of descent (and practically there are 

 no others) must, that their belief and their works shall be consistent, 

 move along the general lines pointed out by Professor Comstock. 



II. 



The great diversity of shape and size among the scales of moths 

 and butterflies is a matter of common remark among entomologists. 

 So nearly infinite, seemingly, are these variations that it is with 

 hesitancy that one undertakes to find order in this chaos. But 

 immensely greater diversity of structure has been found to resolve 

 itself into approximate simplicity, and the "dust of the butterfly " is, 

 after all, a more or less reasonable dust, and exhibits a tolerably 

 rational behavior in its developmental caprices. 



This extreme diversity of character of the scales, and the fact that 

 the scales from one wing may show a great variation in shape and 

 size has deterred systematists from paying them much attention, 

 although this same variety of design, together with the beauty of 

 color of the scales, and their interesting regularity of marking 

 (striation) have made them favorite objects with the microscopists. 

 The suggestion of a writer that the forms of scales might be used for 

 specific characters is said by Westwood to have no weight, as 



