CAVIA CUTLERI. 



11 



apt to be less, or the young will be born smaller and less fully developed 

 (with smaller bodies and shorter hair) , and the period of gestation will 

 be shortened, even to 56 days in extreme cases, the normal period being, 

 as in the guinea-pig, between 60 and 70 days. (See table 4.) If the 

 mother is well nourished and has not borne a litter recently, she is more 

 likely to have a large litter of young. The largest litter recorded (4) was 

 borne by a female 1 year old, which had previously had only 1 young, 

 born 4 months earlier. The recorded date of the birth of each litter of 

 young is given in table 1, together with the interval in days between suc- 

 cessive litters by the same mother, except in cases where the interval is 

 obviously greater than the ordinary period of gestation, and it is to 



TABLE 3. Relation of size of litter and number of litters to time of year. 



Average, 1.47 young per litter. 



2 Average, 2.05 young per litter. 



be supposed that the mother did not breed again immediately. The 

 variation in these day intervals between litters is shown in table 4, 

 from which it appears that the gestation period ordinarily continues 

 from 61 to 69 days, with 63.3 days as an average. However, the 

 periods as recorded can not be relied upon as accurate, except within 

 limits of about 2 days, for the cages were not inspected daily, but only 

 once or twice a week, and when young more than 24 hours old were 

 found in a cage, the estimated age of the young may differ from the 

 true age by 1 or 2 days. Young less than a day old are readily recog- 

 nized as such by the condition of the umbilical cord. 



The 4 original wild-caught females have a somewhat better record of 

 productiveness than their descendants reared in captivity, which indi- 



