162 THE ZOOLOGIST. 



I speak to them. I feed them on hazel nuts and filberts, as 

 well as soft-seeded fruits; and three hazel nuts or one filbert 

 generally constitute their daily quantum of food. In addition to 

 this they get a bit of apple or pear, or perhaps a cherry, accord- 

 ing to the time of year. I found they did not care for apricots, 

 strawberries, or grapes ; a really good sweet pear seemed to be 

 their favourite delicacy. Of smaller fruits they never ate any 

 quantity. 



In 1 880 I attempted to make them open their nuts for them- 

 selves, thinking this would be more natural to them ; until then 

 I had always given them the nuts ready cracked, but this experi- 

 ment was entirely unsuccessful. During the first night they 

 gnawed round holes the size of peas in the nut-shells, and took 

 out all the contents. The next time they gnawed at the nuts 

 without touching the kernel; and in the nights following they 

 made scarcely any attempt at even gnawing them, so that in a 

 short time they became very weakly and thin, and would probably 

 have died of starvation had I not given up my experiment, when 

 they recovered in a few days. Although of different ages, they 

 seemed never to have obtained their food in this state, and thus I 

 was unable to accustom them to it. The experiment might 

 perhaps have succeeded with the female, which was only a few 

 weeks old, had I made the attempt immediately on receiving it ; 

 but I did not do so till a year later, and then without success. 

 Both mice went to sleep on September 23rd, 1879, when the 

 temperature was 0° Reaumur. The bodily heat of the female 

 was less than that of the male. Amongst other hybernating 

 animals the temperature during their hybernation is known to 

 vary considerably, a fact which is very striking in the case of the 

 Ground Squirrel, Spermophilus citillus, and which has been made 

 an object of careful study and observation by Horwarth.* 



The position of the mice during sleep is generally as follows : 

 they curl themselves up, pressing the fore paws firmly against the 

 cheeks, the tail turned forward towards the head, and He in the 

 nest with the back of the head uppermost. Occasionally I find 

 them lying on their backs, the nose pointing upwards. With 

 regard to their weight before and during hybernation, I made the 



* ' Beitriige zur Lehre iiber den Winterscblaf. Abhandlungen der pbys. 

 rued. Gesellscbaft,' Wiirzburg, vii., xiii., uud xiv. Bd. 



