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 = 0.1, M = 2, m = 1 (see Table II). 











TABLE I. 
Three- 
. . Of what gener- | Half of the |abastes Variety No. 2, 
ERIE SS DT oto ation. half-breeds. | pe Bre Dress! 
| side. 
+ | 
1:3 oe ee ee eee Initial number Ne Peta 1, 000 
1.8 | 
| 
| res OOm—— PAG (eS) easieriensn ete Ist generation. TOO) ee ssace il 1, 800 
1.8 | | 
ue oe: l(a) ee 2d generation. 260 | 20 3, 240 
1.8 | 
eS aire IAG (TS) ced) eu d 3d generation. 532 72 Cee 
357.05 = (1.8)!9° comput- | 
ed by log. .°.357,050 = 
PAG (ES) eds tae res sci ageha ae roth generation 35, 688 | 357, 050 
39,347-272 = (1.8)*® 
.”.39,347,272 = A(1.8)!*.| 18th generation|3, 934, 725 | 20, 347), 272 
} 


EXPLANATION OF TABLE I. 
The 2d generation of the half-breeds is found by taking nine-tenths of the pre- 
vious half-breeds, 7. 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), 7. ¢., 
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 18th 
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. 
