I. LIFE PROCESSES 



47 



two to twenty-four young in a single nest have been recorded, 

 but there is no evidence that these young were the progeny of 

 a single female. The average number of fetuses in a large 

 number of gravid females captured in India was 8.1 (Lantz, 

 '10). As many as sixteen fetuses were found in wild Norway 

 females by Zuschlag, by Lantz, and by Donaldson ( '24). Since 

 many fetuses are absorbed in situ, as Huber ('15) and Long 

 and Evans ('22) have shown, the number of fetuses found in 

 gravid females is not indicative of the number of young that 



TABLE 7 



Showing litter production and average size of litters in different generation of 



captive gray rats 



will be born. All of these observations were made on females 

 of unknown ages, and they give, therefore, no evidence regard- 

 ing litter production or the average litter size during the re- 

 productive life of the females. 



Data showing fertility of females in the different genera- 

 tions of captive Grays are given in table 7. 



The breeding record for wild gray females, as given in 

 table 7, may be very incomplete, since some of the females 

 were obviously several months old when they were brought 

 into the colony, and they may have cast young previously to 

 this time. The data for these rats, however, are quite in ar- 



