332 



The Journal of Heredity 



new differentiation must begin, based 

 on the parental instinct. That is, to 

 put it in a simple way, those who are 

 more desirous of children will have 

 more children, and the parental instinct 

 itself will become an element of selec- 

 tive value. It is the fashion for reform- 

 ers to blame the selfish for nt)t having 

 children. That may be good preaching, 

 but it does not get around the fact that. 

 as far as heredity is concerned, we have 

 now a new force working towards iip- 

 proved racial morality and tcnvards the 

 elimination of selfishness. 



Here there is undouljtedly at least 

 one vigorous corrector which must from 

 now on begin to take effect. How far 

 it will go we cannot say. It is a force 

 which, within my observation, has not 

 been sufficiently recognized in discus- 

 sions on the declining birth rate. It is 

 a force si)ringing from one of the most 

 fundamental of instincts, and should 

 soon make itself felt in increasing 

 measure. 



The parental instinct is doubtless 

 bound up with many excellent moral 

 traits, such as domesticity, stability and 

 sym|)athy. There is reason, then, to 

 foresee a better morality in the future, 

 based i^'illv nilly on natural selection. 



Another matter should be kept in 

 mind and that is the fact that the whole 

 nation is not, from a genealogical or 

 natural-history point of view, in any 

 true sense, a melting pot. Classes, sub- 

 races, breeds, and even professions 

 tend to herd with themselves. Most 

 marriages occur within the same social 

 class. For this reason we must study 

 intensively each group separately, trac- 

 ing its rise and decline in quality and 

 quantity. W^e must not think that we 

 can get an idea of the merit of the 

 United States by adding up all the quali- 

 ties of its citizens and dividing by one 

 hundred and ten million ; nor should 

 we despair if a 5% upper crust of edu- 

 cated classes shrank to a 3% through 

 a greater swelling of the unleavened 

 masses. If the upper classes can hold 

 their actual numbers and improve by 

 internal forces, this will be a great deal 

 to be thankful for. The above is writ- 

 ten merely to })oint out that the future 

 is not necessarily so dark as some peo- 

 l)le suppose; it is not a suggestion that 

 active eugenic propaganda is not needed 

 or that governmental and legislative 

 control may not greatly aid in the im- 

 provement of the American people. 



Wanted, Photographs of Twins 



The American Genetic Association 

 desires to communicate with twins living 

 in any part of the world. It has been 

 discovered that twins are in a peculiar 

 position to help in the elucidation of 

 certain problems of heredity. Good 

 photographs at all ages are especially 

 desired in order to determine the degree 

 of resemblance and its persistence 

 through life. Any information, giving 

 the addresses of twins, who arc willing 

 to cooperate with the Association will 

 be keenly appreciated. 



It is known that there are two sorts 

 of twins. (1) The true or "IDENTI- 

 CAL" twins are developed from a single 

 original egg cell which at some very 

 early stage divided to form two indi- 

 vidual beings. These "identical" or 

 "duplicate" twins have a nearly (though 

 never an absolutely) identical germ 

 plasm, are always of the same sex and 



resemble each other to an extraordinary 

 degree. (2) The other kind, "FRA- 

 TERNAL" twins are no more alike 

 than brothers and sisters born at differ- 

 ent times. They "tare developed from 

 two separate egg cells. 



It is fortunate for our knowledge of 

 heredity that there are these two kinds 

 of twins, on account of the chance it gives 

 to study the relative importance of the 

 influence of heredity and of cn\4ronment. 



It is for the study of this funda- 

 mental question of the degree of influ- 

 ence cxepted by environment as com- 

 pared with that due to heredity that 

 the cooperation of the twins of the 

 world is solicited and any publicity 

 given to this notice by the press will 

 be of great assistance. 



All communications should be di- 

 rected to the American Genetic Asso- 

 ciation, Washington, D. C. 



