COMPUTATIONS OF EFFECTS. 



177 



5. Computation of the Effects of Different Degrees of Positive Segregation 

 Cooperating with Different Degrees of Segregate Survival. 



Of the tables which are herewith presented Table I is an arithmet- 

 ical computation, showing the number of half-breeds as contrasted 

 with the pure-breeds, when nine-tenths of each variety form unions 

 among themselves and double with each generation, while the off- 

 spring of the one-tenth that form mixed unions simply equal the 

 number of the parents by which they are produced ; in other words 

 when c o.i, M = 2, w = i (see Table II). 



TABLE I. 



EXPLANATION OF TABLE I. 



The 2d generation of the half-breeds is found by taking nine-tenths of the pre- 

 vious half-breeds, i. e., 100 X 0.9 = 90, and one-tenth of the previous pure-breeds 

 (the one-tenth that form mixed unions), minus one-tenth of the previous half- 

 breeds (because one-tenth of the half-breeds consort with an equal number of 

 pure-breeds, and so produce not half-breeds but three-quarter breeds), /. e., 

 180 10 = 170. Adding these two sums together we have 90 + 170 = 260 = 

 the 2d generation of half-breeds. 



As in this table the computation commences without any half-breeds, the fol- 

 lowing generations of half-breeds are all a little less than one-tenth as large as the 

 corresponding generations of pure-breeds. When, however, we come to the i8th 

 generation the difference is less than one in a million, and we may consider the 

 result as practically corresponding with the formula for the nth generation given 

 in Table III. 



