130 CARNEGIE INSTITUTION OF WASHINGTON. 



FORCING PIGMENTATION IN ALBINOS. 



Dr. Riddle, in collaboration with Mr. Victor K. LaMer, has been able 

 to induce the formation of melanin pigment in the choroid of a species of 

 dove in which such pigment is not ordinarily produced. They show 

 that free oxygen is necessary for the process. 



PHYSIOLOGY OF REPRODUCTION. 

 EGG-PRODUCTION AND SKIN-COLOR IN FOWLS. 



Dr. Blakeslee, who discovered two or three years ago that yellow 

 pigment on the ear-lobes and shanks of White Leghorn fowls was 

 inversely correlated with fecundity, has pubUshed a fuller paper, with 

 statistical analysis by Dr. Harris, on this subject. It appears that the 

 percentage of yellow (as measured by the color top) in the ear-lobe 

 during October is closely inversely correlated with the mean annual 

 egg-production of any bird. The correlation is 0.55. The result is of 

 great practical importance, since by it one can tell in October without 

 trap-nesting which birds have been the heaviest layers during the 

 past year. Birds showing only 10 to 20 per cent of yellow in their 

 eai'-Iobes in Octobes- will have laid at the end of the following year on the 

 average about 185 eggs; those exhibiting 55 to 65 per cent yellow will 

 have laid on the average only about 130 eggs. This result is believed 

 to be due to the circumstance that the growth of the eggs in the ovary 

 abstracts yellow pigment from the body- tissue, or precludes its being de- 

 posited there. In any case the discovery, now abundantly demonstrated, 

 is of great practical, and not a little theoretical, importance. 



RELATION BETWEEN NUMBER OF OVULES PER POD AND FERTILITY IN BEANS. 



A study of over 150,000 pods of beans was made to determine the 

 degree of relationship between the number of ovules per pod and the 

 capacity of the pod for maturing its ovules. The conclusion is that 

 there is a negative relationship between these two qualities such that 

 the greater the number of ovules the smaller the proportion that will 

 develop into seeds. The correlation is not a very close one, however, 

 being of the order of about 2 per cent. This investigation and that 

 recorded in the following paragraph were made by Dr. Harris. 



RELATION BETWEEN NUMBER OF PODS PER PLANT AND INDIVIDUAL 

 SEED-WEIGHT IN BEANS. 



From 15,897 bean plants 78,975 seeds were weighed and it was 

 determined that uniformly in each of 27 cultures there was a positive 

 correlation between the number of pods on the plant and the average 

 size of the beans produced. The size of the correlation varied from 

 +0.005 to +0.339, with a mean of 0.159 ±0.012. This result agrees 

 with others secured earlier that permit the conclusion that, on the 

 average, the larger the number of pods on the navy-bean plant the 



