No. 636] GUINEA I'K.s AXD lUBKRCVLOsls 



21 



tioii, after making certain assumptions in regard to the 

 frequency of the disease in the whole population, and 

 making allowance for the age of the children, many of 

 whom had not reached the age of greatest danger. This 

 correlation is about the same as that between parent and 

 offspring in characters such as height, weight, eye color, 

 etc., which are largely or wholly dctiTmiiKMl by heredity. 

 The correlation between husband niul wif.' was oidy .24 

 and even much of this, the author fouiul rrason for at- 

 tributing to assortative marriage. 



Goring 's study was made with the families of British 

 convicts. He also found a correlation of about .50 be- 

 tween parent and offspring but no correlation (—.01) 

 between husband and wife. The only assumption that 

 had to be made in this case was a correction for the age 

 of the children. 



We are acquainted with no experimental work bearing 

 on this question. 



Material 



The present paper describes the results of experiments 

 on certain inbred and crossbred stocks of guinea pigs. 

 All of the animals used were a by-product of experiments 

 on the effects of inbreeding which have been carried on 

 by the Bureau of Animal Industry of the U. S. Depart- 

 ment of Agriculture since 1906. One of the authors 

 (Wright) has been in charge of these experiments since 

 1915. A detailed report on the results is soon to be pub- 

 lished. A brief summary will suffice here. 



Twenty-three families of guinea pigs were maintained 

 for a number of years by mating exclusively brother 

 with sister among the descendants of tw^enty-three orig- 

 inal pairs. In sixteen cases (including families 2 and 1^^ 

 of those tested for resistance to tuberculosis) both of the 

 original parents came from a stock which had already 

 been maintained for twelve years without the infusion of 

 fresh blood, by the Experiment Station of the Bureau of 

 Animal Industry. In the remaining families, including 

 families 32, 35 and 39, the original females came from 



