118 INTRODUCTION TO EVOLUTION 



contained antigen (serum) diluted 1:1; tube 3 antigen diluted 1:2; tube 4 

 antigen diluted 1:4; and so on in doubling dilutions. The antiserum added 

 to each tube had been obtained by pooling antisera from four cocks all of 

 which had been inoculated with domestic rabbit serum. The numbers 

 along the left side of the graph represent the turbidity developed (in terms 

 of galvanometer readings of the photronreflectometer). The solid line of 



DOMESTIC RABBIT 

 COTTONTAIL 



-O O-BEEF 



-—-•-GUINEA PIG 



-ALBINO RAT 



MAN 



5 6 7 8 9 10 

 ANTIGEN DILUTIONS 



FIG. 6.3. Serological relationships of lagomorphs to sev- 

 eral other mammals. Turbidity (photronreflectometer) tests. 

 (From Moody, Cochran, and Drugg, "Serological evidence 

 on lagomorph relationships," Evolution, Vol. 3, 1949, 

 p. 28.) 



the graph connects points representing the turbidity formed in each of the 

 tubes of the homologous series, i.e., the series containing successive dilu- 

 tions of domestic rabbit serum. It will be noted that this curve includes a 

 greater area than do any of the other curves. The curve representing the 

 reaction obtained with the other lagomorph included in the study, the cot- 

 tontail rabbit, is second in magnitude. The other curves subtend much 

 smaller areas. Of these the reaction with beef serum, representing Order 

 Artiodactyla, is greatest, the reactions with the sera of representatives of 



