Xo. 635] SHORTER ARTICLES AND DISCUSSION 545 



per cent, related, and the part of the inbreeding due to relation- 

 ship between his sire and dam is 59.82 per cent, of the actual 

 total inbreeding. 



In Fig. 1 the inbreeding curve and the relationship curve are 

 plotted, based on the figures given in Table I, the former as a 

 solid line, the latter as a broken line. The smooth curve indi- 

 cates the maximum inbreeding curve; the broken line, that 

 divides the area in two equal halves, indicates the maximum 

 relationship curve. These four curves taken together give a 

 fairly good graphical demonstration of the facts in question. 



1. The area OABX in relation to the area OAEX gives the 

 proportion of the actual to the maximum degree of inbreeding: 

 The total inbreeding coefficient. 



2. The area OACX in relation to the area ODFX indicates 

 the proportion of the actual to the maximum degree of rela- 

 tionship: The total relationship coefficient. 



3. The area OACX in relation to the area OABX gives the 

 proportion of the inbreeding that is due to relationship: Th> 

 total relationship inbreeding index. 



In bringing all measurements of degrees of inbreeding and 

 relationship to the same scale and using areas as the measures 

 we get a uniform and significant series of coefficients that nu- 

 merically express the degree of inbreeding and relationship in 

 a given pedigree. Tage Ellinger 



SOME OBSERVATIONS CONCERNING THE 

 PERIODICAL CICADA 



During the recent visitation of the periodical cicada, their 

 great abundance on the writer's home grounds at Vinson Sta- 

 tion, Va., afforded an excellent opportunity to observe some of 

 the habits of these interesting insects. During the months of 

 January, February and March, the writer was engaged in clear- 

 ing off all trees and brush from several lots immediately adjoin- 

 ing his home grounds. In the course of this work, several large 

 oak trees were completely dug up by the roots. Even during the 

 winter months, many of these benumbed creatures were encoun- 

 tered in their burrows in the soil around the roots. As warmer 

 weather approached, their burrows became more numerous in 

 the soil and it was evident that they were approaching the 

 warmer, uppermost layer in ever-increasing numbers. Finally, 



