118 RAYMOND PEARL AND WILLIAM FREEMAN SCHOPPE 



record made of the chicks which developed from oocytes pro- 

 duced by these regenerated ovaries. Unfortunately, all the 

 records of this experiment were lately destroyed by fire, and 

 hence cannot be reported. The writer regarded this experiment 

 as perhaps the most interesting and fundamentally significant 

 for the problem of genetics of any of his work, with poultry. Men- 

 tion is made of the matter here in the thought that possibly some 

 one so situated as to be able to carry on work of this sort, which 

 the writer no longer is, may care to repeat the work. 



SUMMARY 



The chief results of this work may be stated as follows: 



1. Detailed counts are given of the number of visible oocytes 

 on the ovaries of thirty-six birds, including various breeds of 

 domestic fowls, water-fowl, and wild birds. 



2. In general the mean number of visible oocytes on the ovaries 

 of different kinds of birds reflects the normal fecundity or laying 

 activity of the same kinds of birds. This relation does not hold 

 with any exactitude or regularity for differences in fecundity 

 between individual birds. 



3. In Barred Plymouth Rock fowls the number of visible 

 oocytes increases with advancing age of the bird, within the age 

 limits of six months and thirty-seven months. The probable 

 explanation of this phenomenon is given. 



4. By removing a portion of the ovary and causing it to 

 regenerate, the total number of oocytes developing to visible 

 size in the lifetime of the bird is caused to increase from 33 to 

 68 per cent over the number which develop in the normal, unop- 

 erated bird. This increase is shown to be statistically significant. 



