KELLOGG AND BELL 



confluent ; i individual has i 1 and i r lacking and 2 r -f 3 r conflu- 

 ent ; i individual has 2 r and 3 r lacking and 2 1 -f 3 1 confluent ; 

 i individual has i 1 and i r lacking and 2 1 + 3 l confluent ; i indi- 

 vidual has i 1 i r , 3 l and o lacking and 2 r + 3 r confluent ; 2 indi- 

 viduals have i 1 lacking and 2 r + 3 r and 2 1 -f 3 1 confluent ; 2 

 individuals have i 1 and 3 1 lacking and 2 r -f 3 r confluent ; 3 indi- 

 viduals have i 1 and i r lacking and 2 r -j- 3 r and 2 1 -f 3 1 conflu- 

 ent ; i individual has 3 1 lacking and o a line ; i individual has 

 i 1 , i r and 3 r lacking and o a line ; 2 individuals have 3 1 and 3 r 

 lacking and o a line ; 4 individuals have i 1 , i r , 3 1 and 3 r lacking 

 and o a line ; i individual has i 1 , i r , 3 r and o dim and 3 1 shifted 

 toward 4. 



The variation in the number and disposition of these protho- 

 racic spots consists, as may be noted from an inspection of the 

 above table, of the addition (never more than two spots) or sub- 

 traction (never more than five spots) of spots ; of the coalescence 

 of two adjoining spots on either or both sides ; of the substitu- 

 tion of a small line for the spoto (spot 5, fig. 56) in the middle of 

 the series ; and of many combinations of any two or several of 

 these conditions. The modal condition is that when the series 

 is composed of five spots, a middle one (o), with two on each 

 side (2 1 , 4 1 and 2 r , 4 r respectively). The next most frequent 

 conditions are when the series consists of but four spots (the 

 middle spot, o, of the modal condition being absent), and when 

 the series consists of seven spots, namely the middle one (o) 

 and three on each side (i 1 , 2 1 , 4 1 and i r , 2 r , 4 r ). Another fre- 

 quent condition is when all nine spots (of the hypothetical con- 

 dition of symmetry) are present with two on each side (2 1 +3 1 

 and 2 r -f 3 r respectively) confluent or fused. The remaining 

 fifty-six conditions of this prothoracic series of spots as noted 

 in the lot of 221 individuals are represented by from one to 

 eight cases each. That these variations can have a life and 

 death selective worth seems inconceivable to us, and yet they are 

 of the general character on which new species (in the teeming 

 genera of insects) are established. That such diverse condi- 

 tions of this prothoracic pattern have survived through their im- 

 mature life until the insects have reached maturity is evidence 

 incontrovertible that the selective agents have overlooked as 



