466 



MISSES K. FOOT AND E. C. STROBELL 



Table 11. — Lengths of the introraittent organs in the 18 males from the- 

 Backcross (i.e. Fi $ X pure variolarius <$), side by side with the 

 inheritance of the E. variolarius genital spot. A comparison demon- 

 strates again that these two exclusively male characters are not linked 

 in inheritance. Photos 62-66. Plate 47. 



Photos. 

 62 



63 



64 



65 

 66 



Genital spot. 

 1st (upper) bug JE. variolarnis. 

 2nd „ ditto. 



3rd „ intermediate. 



Ath. „ ditto. 



1st (upper) bug E. variolarius. 



2iid „ ditto. 



3rd „ ditto. 



4th „ ditto. 



1st (upper) bug E. variolarius. 



2nd 

 3rd 

 4th 

 5th 

 6th 



ditto, 

 intermediate. 

 E. variolarius. 

 intermediate. 

 E. variolarius. 



E. variolarius. 



1st (upper) bug E. variolai-ius. 

 2nd ;, intermediate. 



3rd ,, ditto. 



Intromittent organ. X 20 diams. 



Intermediate 112| mm. 



E. variolarius 105 „ 



Intermediate 128| ,, 



ditto 117 „ 



Intermediate ■ . 110^ mm.. 



ditto 116 „ 



E. variolarius 106 „ 



Intermediate 107 „ 



Intermediate 115 mm.. 



ditto 112^ „ 



ditto 122i „ 



E. variolarius 102 ,^ 



Intermediate 119 „ 



ditto 118 „ 



Intermediate 113 J mm.. 



Intermediate 

 ditto 

 ditto 



1141 mm. 

 116i „ 

 106^ „ 



Mean length of intromittent organ , 113'47 mm. 



It is an interesting fact that Mendel's Law of Heredity owed its inception^ 

 in part to an analytical study of a size-character — the character which has- 

 proved on further investigation to be the greatest stumbling-block to an, 

 unqualified acceptance of the law as a wholly satisfactory explanation of the 

 problems of heredity. In his original work on tall and dwarf peas, Mendel 

 found that two lengths so far apart as 6 ft. and Ig ft. acted as unit characters,, 

 and these characters showed dominance and segregation. 



More recent work on size-relations has led to an accumulation of facts- 

 showing that in the majority of cases dominance and segregation in the 

 Mendelian ratios of 1-2-1 are not present ; and many Mendelians have- 

 made ingenious efforts to reconcile these facts with their conception of 

 Mendelism by adding a superstructure to Mendel's original law, which has- 

 called forth an earnest protest from certain investigators. 



elastic was the first Mendelian to demonstrate a case in which dominance- 

 and segregation were found to be absent where a length-character was 

 carefully studied. He crossed the long-eared lop rabbit with the ordinary 

 short-eared type, and found the Fi generation with ears intermediate ia 



