ANOMALIES IN FECUNDATION AND GESTATION. 



SUPERFECUNDATION. 



Superfecundation is the fertilization of two or more ova, one 

 after another, during one estrual period. When two or more ova 

 are discharged during a given estrual period, one or more of them 

 is fertilized as the result of one copulation, another ovum as the 

 result of a subsequent copulation. If the two or more copula- 

 tions are made by the same male, the evidence of superfecunda- 

 tion is wanting. When two or more males of different types, 

 breeds or species copulate with the female and each fertilizes cer- 

 tain ova, the evidence of superfecundation becomes marked. The 

 phenomenon may occur in any female in which two or more ova 

 are discharged during a given estrum. If all the ova are simul- 

 taneously discharged, superfecundation is less probable, except 

 the copulations follow each other shortly. 



Superfecundation is most common in the bitch, in which there 

 is a prolonged estrum, probably successive ovulations, and very 

 commonly repeated copulations with dogs of various breeds. As 

 a result, it is not rare to find the young of a given litter showing 

 unmistakable evidences of varying male parentage, some of the 

 young being evidently of one breed, others of another. 



In such biparous animals as the sheep and goat, such results 

 are always possible, but the opportunity for copulation by males 

 of different breeds is not usually offered. 



In the mare, in which twins are rare, there are records of a few 

 cases in which a mule and horse foal have been born as twins, 

 the result of closely succeeding copulations of a stallion and an 

 ass. The two services may be separated by several days, not 

 exceeding the duration of the estrual period. Lanzillotti-Buo- 

 santi records a case where an interval of eight days elapsed be- 

 tween the service by the stallion and the ass. 



SUPERFETATION. 



Superfetation differs from superfecundation in that fecunda- 

 tion occurs in an animal already pregnant, due to copulations 

 during two separate estrual periods. The phenomenon depends 



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