1883., 
Correspondence. 
DESCENT. 
243 
To the Editor of the Journal of Science. 
Sir, — How far has isolation operated on Descent ? Would not 
the separation of one or a few pairs of individuals from the 
congregated species cause a more decided and rapid develop- 
ment of variations than if left with a large number of their 
own race ? 
There are many items possessed in general which, however, 
every individual does not unfailingly inherit, but this is speedily 
rectified in the offspring by reason of overwhelming oppor- 
tunities. But if one pair were isolated the only influence at 
work would be contained in the parents ; the vigour of their par- 
ticular constitution would have full play, and their peculiarities 
would be inherited without any fear of counteraction by the 
generalities of the species, variations consequently arising much 
more rapidly. 
There is no other explanation in domestic species, but may it 
not have taken place on a much more important scale ? Here- 
ditary fancies will no doubt help to keep up a species, though 
very often I have noticed pigeons decidedly prefer another variety 
to their own. — I am, &c., 
D. Y. C. 
[Our correspondent’s views seem essentially the same as those 
of Dr. Moritz Wagner, discussed in our last volume (p. 460) 
under the title “ Evolution by Segregation.” — Ed.] 
THE COST OF SANITARY REFORMS. 
To the Editor of the Journal of Science. 
Sir, — On reading a recent article on “ Health in Health Resorts,” 
from the pen of Dr. B. W. Richardson, I am forcibly reminded 
that enthusiasts often forget to count the cost of their projects. 
We are told that it is possible to make use of water-carriage for 
sewage without having our rivers polluted. For this purpose the 
learned author would have “ floating tanks on the canal or river, 
in or connected with a steam barge which should pump from the 
town its sewage into the receiving-tanks, and then, when charged, 
