642 THE POPULAR SCIENCE MONTHLY. 



feel that it is a duty they owe, not only to themselves, but also to their 

 country, to propagate a pure race. . It is repugnant, at first thought, 

 to speak of " breeding " men and women, but this very repugnance to 

 handling a subject surrounded by so much delicate reserve has been 

 largely conducive to the race-degeneration. We know that the race 

 should be improved ; every year, as has been shown, pours its rapidly 

 increasing mass of impure blood into the general current. A man 

 with one or more hereditary diseases on his side, and a woman with a 

 like number among her ancestry, make it almost impossible for their 

 offspring to escape. 



We know that the race can be improved, as is shown by analogies 

 among the lower animals. How paradoxical it seems that a man who 

 would scout the idea of breeding his stock to diseased animals should 

 yet without a word of opposition see his children marry into families 

 where the hereditary taint is marked. Yet such is undoubtedly the 

 fact. Ignorance must be the prime cause of much of this misery ; for 

 the certainty with which some diseases reproduce themselves in suc- 

 ceeding generations is a fact which can be proved, and not a mere set 

 of coincidences as many suppose. 



The theory that healthy blood on one side of the house is sufficient 

 to counteract the diseased of the other is, unfortunately, fallacious. 

 The predisposition to hereditary disease will often survive many in- 

 fluxes of pure blood, and the currents may, like the clear and sparkling 

 Rhone emerging from Lake Geneva, and the dirty-gray Arve from the 

 glaciers, run side by side for a while, separate and distinct, but at last 

 they mingle, forming one turbid stream. 



- 



EVOLUTION IN ARCHITECTURE. 



By FRANCIS H. BAKER. 



THE disciple of Darwin labors under one disadvantage. The peri- 

 ods necessary for maturing the changes which he investigates 

 being so immeasurably superior to those relating to ordinary mun- 

 dane affairs, he can not verify the sequence of the events by the inde- 

 pendent testimony of contemporary history. It would be interesting 

 to apply the theories of development and natural selection to some 

 department of knowledge in which we could have that aid. 



Human society is so largely subject to the influence of emotions 

 which appear to have little or nothing in common with the orderly 

 operation of natural laws, and its course is so checkered with action 

 and reaction, that it is often difficult to follow any particular line of 

 progress for a length of time. Examples of regular development are, 

 however, not wanting, and one of the most striking is to be found in 

 the history of architecture. To a person ignorant of such history 



