24 BIOLOGY 



female is a very sensitive reaction which may be stimulated or 

 depressed by a variety of conditions — and for this reason a 

 rather wide range of results is to be anticipated. 



At the beginning of ovulation Sobotta and Burckhard ('10) 

 find on the average a total of thirteen ova in both fallopian 

 tubes. In their series, Long and Evans ('22) found an average 

 of 9.6 ova in both tubes. The largest litter we have noted in 

 the common Albino contained eighteen. Several such litters 

 have appeared. 



The number of ova found in the oviducts is only about 90 

 per cent of the number of corpora lutea formed, (Long and Evans 

 '22). Moreover, these observers found that the average size 

 of the litters was 6.9, so that about one-third of the ova formed, 

 (9.6) failed to produce young. When, therefore, the number of 



TABLE 4 

 Table showing length in hours of the component parts of the oestrous cycle of the rat 



One 



Two and Three. . . 



Four 



Five (Dioestrous). 



young born is considered, the foregoing relations should be held 

 in mind. The majoritj^ of albino females do not produce more 

 than four or five litters, although occasional animals may pro- 

 duce three times as many. 



Size of Utters. The usual size of the litters is indicated in 

 table 5. 



It should be noted that generally these determinations have 

 been based on the first five litters and do not extend through the 

 possible breeding period of the female. 



The litter size does not appear to be influenced by season, 

 (King and Stotsenburg '15). It may depend however on the 

 position of the litter in the litter series as can be seen from 

 table 6. 



