60 MAYNIE R. CURTIS. 



to them. Table I. showed that some pullets before they were 

 seven months old had produced as many as three eggs with more 

 than one yolk, while 80 per cent, of the flock had laid only single- 

 yolked eggs. Also the data collected for the investigation on 

 egg size contribute some evidence on this point. All of the eggs 

 laid by 22 birds during their first two laying years were opened. 

 Only 5 of these birds ever laid an egg which had more than one 

 yolk. Four of these five laid one or two double-yolked eggs 

 among their first seven. Two of the four never afterward laid 

 an abnormal egg. The others, however, produced two (in the 

 first case) or three (in the second) double-yolked eggs when they 

 were mature. Out of the flock of 22 only one bird w r hich had 

 not produced double-yolked eggs at the beginning of the first 

 laying period produced one after she was mature. This indicates 

 that individuals differ in the stability of the regulation of their 

 reproductive processes, and if these processes in an individual 

 are unstable, irregularities are most likely to occur among the 

 first eggs produced when the bird begins to lay while young. 

 Also different individuals show varying degrees of instability, 

 so that some may also show irregularities later. 



THE RELATION OF THE PRODUCTION OF DOUBLE-YOLKED EGGS 



TO OTHER FORMS OF ABNORMALLY RAPID EGG 



PRODUCTION. 



A study of the nature of the disturbances which cause the 

 formation of double- and triple-yolked eggs is limited by the fact 

 that as yet we do not fully understand the nature of the regulation 

 of the egg-forming processes which cause the production of 

 successive single-yolked eggs. One of the earliest and most 

 extensive investigations of the physiological processes involved 

 in egg formation was that of Coste. 1 He made important ob- 

 servations on the time spent by the egg in the oviduct. Similar 

 observations are also recorded in a previous paper from this 

 laboratory. 2 Published and unpublished observations show that 



1 Coste, M., "Histoire du developpement des corps organises," Tome I., Paris, 



1874- 



2 Pearl, R., and Curtis, M. R., "Studies in the Physiology of Reproduction in 

 the Domestic Fowl, V., Data Regarding the Physiology of the Oviduct." Jour. 

 Exp. Zool. Vol. 12, pp. 99-132. 



