181 
Intergenerant pra 
Groups. k 
Ist generation + b produces 9 
n 2 } 2nd generation. 
a 
MY 
2nd generation ... e + 4 b . 
Far «d } 3ra generation. 
3rd generation ... a + 
€ [i 
: A l 4th generation, 
The significance of the word “or” in the above table is 
that different grou pem i are given to the children accord- 
ing as to w ether “ c., &c., is male or female. The above 
second generation acco rding to the four second groups 
(e, f, g, h). Their progeny again cross-marry in the third 
direction, and have been the mean of the whole, producing a 
monotypic S ene because, as Romanes points out, na- 
tural selection per can never produce polytvpic, but onl 
monotypic evolut The marriage laws of the Australian 
aborigines are seen, ipfius to favor the maintenance of a 
uniformity of type 
IsoLation.—As ET been mentioned, een is a Rapp 
term having species, sub-species, forms, an a 
genus the isolation of the Australian Xy has honi a 
marked one, and, comparatively speaking, a complete one, 
à us, 
essentially discriminate. It has been pointed out that that 
sub-species of Bis ogamy called ae selection, which is the 
exclusive breeding between those bes t adapted to their en- 
vironment, is ineffective to produce divergence of type un- 
assisted, except in one Quern M that its effects may be 
cumulative ; Or, as writes, it may be occupied with 
ears 
checking, guidi ing, and re heren ii: a progressive 
