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THE AMERICAN NATURALIST [Vol. XLV 



instance, she was seen to clasp the male. If he is not ag- 

 gressive, she throws herself before him in a crouching 

 position, a procedure which she repeats until he takes 

 notice of her. Again, she may strike his head, as though 

 fighting, until he follows her. A female in full heat is 

 much more active and less pugnacious than at other 

 times. 



We find the anomaly of mammals eating their young 

 carried to an extreme in the case of brown rats kept in 

 confinement. My records show a large per cent, eaten, 

 almost fifty, which has much to do with the number of 

 litters per year, consequently the number of young. 

 This infanticide has usually been attributed to the male, 

 but the young are eaten whether the male is or is not 



