906 



ME. H. H. BEINDLBY OS THE KEGENEKATION [NoV. 30, 



The examination took no account of the sex of immature 

 individuals, because of the very great difficult)^ or impossibilit}'^ of 

 rightly ascertaiuing it without making a dissection in each case. 



In the great majority of cases only one of the six legs bore a 

 four-jointed tarsus, though many individuals possessed the 

 abuormality on more than one leg. This point was examined 

 in detail iu rather more than one thousand young and adult 

 individuals of both sexes distributed among three species, with the 



following result :- 



Table C. 



P. americana 

 P. australas'uB 

 8. orientalis .. 



Number of 

 individuals 

 examined. 



203 

 116 

 733 



In all four species the postei'ior pair of legs was the most 

 frequently affected. The following table gives the percentage 

 incidence of four-jointed tarsi amoug the three pairs of legs : — 



Table D. 



The abnormal tarsi occurred indifferently on the right and left 

 sides — thus, in 1329 cases in S. orientalis, 661 Mere on the right 

 and 6GS on the left side. 



Having set forth the preliminary results obtained, it becomes 



