146 CARL R. MOORE 



litter and while separated for observation. It is beyond ques- 

 tion that the early castrated male rats which have received im- 

 planted ovaries display a maternal behavior towards the young. 

 The two normal female controls (III and IX) gave birth to lit- 

 ters of young during the course of the experiment and often the 

 mother with young was allowed to remain in the common cage. 

 It was repeatedly observed that the feminized male rats would 

 enter the nest with the mother or without her, would nestle the 

 young and repeat exactly the behavior of the mother when the 

 young attempt to suckle. If the litter is a large one and the 

 young from seven to ten days old, the mother will assume a 

 peculiar position to enable the young to suckle; the abdomen is 

 arched and both the fore and hind-legs are widely separated as 

 the young wriggle around underneath in search of teats. The 

 reaction is quite characteristic. This reaction was displayed 

 absolutely typically by the feminized males. The normal male 

 rat and the masculinized females are seldom if ever, seen on or 

 near the nest,^^ and apparently they take no interest in the 

 young. The following observations from the note-book will 

 illustrate the phenomenon and its frequency: 



April 30, 1918. Normal female gave birth to litter of six young. 



May 1. Normal male and masculinized females had been removed 

 from cage leaving mother and three feminized males. Feminized male 

 V showed all apparent reactions of mother — persistently occupied nest 

 of young with mother and apparently young were attempting to 

 suckle, no teats developed, however, and young could not suckle. 

 Fem. male licked 3'oung, tucking same under him, when attempt to 

 remove him from young would attack and bite. Evident mother 

 instincts, would arch abdomen for young to attempt to suckle. Prof. 

 Lillie sees behavior. 



May 2. Observed several times during day (normal male now in 

 cage), feminized male IV several times on nest with mother — it lies 

 down with young allowing them to search for teats, arching abdomen 

 as they work around in search of teats. Normal female (mother) had 

 to lie across body of fem. male to get to young, three suckhng mother, 



" The cage in which the litter was confined was 26 x 18 x 12 inches, made of 

 galvanized wire, sides and top, and a movable bottom. The nest was made 

 from paper torn up by the mother and placed in one corner of the cage. When 

 the mother leaves the nest, especially during the early life of the young, she 

 almost invariably covers it with small loose pieces of paper from the edge. 



