Aug. 1910.] The Common Mole. 11 



or gave indisputable evidence of having recently born their 

 young. The first specimen of this latter number was trapped 

 February 27, the last April 20. 



It would appear, then, that in this vicinity (Manhattan) the 

 young are produced within a period of three to five weeks, 

 mainly in March and early April. The period of gestation 

 must be comparatively short, for signs of pregnancy did not 

 appear until about five weeks before the first females gave 

 evidence of having borne their young. My data on this point 

 are not full enough to warrant a positive conclusion; for, of 

 the twenty-five moles trapped during the months of December 

 and January, and up to February 27, only five were females. 

 This fact itself may be significant of a period of seclusion or 

 less activity among the females during the period of preg- 

 nancy. 



While, as stated above, the normal number of young is four, 

 there were two cases in which there was but a single foetus in 

 one horn of the uterus ; the other horn contained two, as usual. 

 In one instance also there were five fceti. 



That development after birth is very rapid is shown by the 

 litter of young moles referred to in the last item in the ac- 

 companying table. These were discovered in a nest of dry 

 grass under some sod, April 22. The sod had been turned 

 over by the plow only about ten days previously. Although 

 still perfectly hairless, these young moles weighed one ounce 

 each from one-fourth to one-third the weight of the adult. 



Results of the Examination of 38 Female Moles for Breeding Conditions. 



Date. Conditions for breeding, number of embryos, etc. 



Dec. 11, No signs of pregnancy. 



Dec. 17, No signs of pregnancy. 



Feb. 6, No signs of pregnancy. 



Feb. 20, No signs of pregnancy. 



Feb. 22, No signs of pregnancy. 



Feb. 27, Uterus congested; very evidently pregnant. 



Feb. 27, Uterus very much congested, but foeti not distinguishable. 



Feb. 27, Uterus very much congested, but foeti not distinguishable. 



Mar. 6, Uterus very much congested, but foeti not distinguishable. 



Mar. 7, Three foeti in one horn of uterus, two in the other; scarcely 

 distinguishable. 



Mar. 8, Pregnant. Number of fceti apparently four; scarcely dis- 

 tinguishable. 



Mar. 8, Two fceti in each horn of the uterus; very small. 



Mar. 8, Pregnant, but number of foeti not distinguishable. 



3Iar. 18, Pregnant, but number of foeti not distinguishable. 



