W. E. Agar 



309 



(-J ratio). The latter ratio was found to be the more useful. In the 



male the ratio p, as in the female, was employed. In both sexes, 



length of body was taken as a straight line from front of head to base 

 of spine (Fig. 2). 



Fig. 2. Female D, pulex. A, B, C, the three dorsal abdominal pro- 

 cesses ; a — a', b — b', the lines along which the measurements of 

 processes A and B were made ; X — Y, the line along which the 

 body length was measured. 



Like most other sexual characteristics, the abdominal processes do 

 not attain their full development until maturity. The new-born female 

 has no recognisable trace of process C, and only slight sinuosities of the 

 dorsal outliiie to represent A and B. By the time the adolescent stage 

 IS reached, all three processes are well developed, but still much smaller 

 than in the adult, not only absolutely, but also relatively to the body 



