U. K. Nabours 6^ 



allelomorphs) SS and // from which it was itself derived. It also 

 breeds true, matings (524), (525), (526), and (527). 



Obviously it cannot be determined in this case, mating (472), 

 whether the female gave an unusual gamete containing the factors for 

 B and S and the male gave the gamete containing a factor for the 

 modified /, or whether an abnormal gamete from the male carrying 

 the factors for S and the modified / fertilized a normal gamete from the 

 female carrying the factor for B. It is also not possible for me to 

 suggest the means by which the combination, or linkage, was accom- 

 plished. 



In mating (507), O^S' x CI (see table), another similar combination 

 occurred, with C involved instead of B as in mating (472). Here an 

 individual combining the C, S, and modified / patterns (CIS) appeared 

 among the otherwise approximately normal expectation of CC 14, CI 9, 

 CS 15, and 7>Si 14. The / and S in this mating had come through one 

 generation from the mating (472) which produced the original BIS (see 

 table). This CIS was in all observable respects similar to the other CIS 

 individuals produced by descendants of the original BIS aberrant form. 

 It died before reaching adult stage. When this CIS nymph, mating (507), 

 was first observed, during its third instar, consideration was given to 

 the possibility of its having been introduced into the breeding jar acci- 

 dentally from some contemporaneous jar containing CIS, as matings 

 (486), (510), and others. However, careful examination of the other 

 breeding jars containing CIS disclosed that none of these had arrived 

 at the third instar stage, and, furthermore, this jar (507) had not been 

 near enough these jars to make it likely that any accidental exchange 

 might have been made. However, there remains the bare possibility of 

 an accident in this case. 



It appears that this strain of /, or S, or both, is subject to abnormal 

 behaviour, and that the linkage, or modification, is permanent, thereby 

 making a new and true breeding pattern. It may be that some of the 

 numerous multiple allelomorphs in Paratettix have been developed in a 

 similar way. The form QQ (see plate in second instalment) which so 

 much resembles the form CG, may hava secured the redness of its legs 

 from some other fofm, just as the SS, in the experiment, mating (472), 

 has become greatly modified through linkage with I. (In the new 

 form, IS, the *Si pattern is more conspicuous than the I pattern.) 



I am under obligation to Mr A. W. Bellamy (1910 — Fellow in 

 Zoology in the University of Chicago) for valuable help during the 



