8 Adams, Epidemic of the Coniinon and Lesser Shreu> 



the decided opinion that the original hirsuteness had 

 never been lost. 



These points being noticed the question naturally 

 arose as to what had become of the adults. Clearly, if 

 my series was sufficiently representative, and if my 

 examinations of their internal anatomy were not faulty, 

 the adults must have all died ; and they must have died 

 off as soon as they had done their part in the breeding 

 season ; or to state the matter in another and more 

 startling form, — the autumnal " epidemic'' is due to 7iothing 

 more than old age ; old age in the case of the Common and 

 the Lesser SJirew being readied in, roughly, thirteen or 

 fourteen months. 



Considering the novelty of this proposition it occurred 

 to me that, in spite of all my care, some at least of the 

 seeming winter juveniles might really have been adults, 

 that the hairy tails ivere clothed with a winter pelage, 

 that the vaginas of the females Jiad closed again after 

 breeding, and that the genitalia of both sexes had 

 atrophied practically to extinction. 



Therefore, as a test that would either refute or confirm 

 the points in doubt, I have drawn up from my records the 

 following Chart showing the average size of the two 

 species throughout the cycle of a year, month by month. 

 In these I have taken the head-and-body measurements 

 only as being most useful, neglecting the tail measure- 

 ments which I found to vary independently of age, sex or 

 season, and it will be seen that, judging by comparative 

 size also, the winter specimens are immature. 



In order to secure uniformity in the framing of the 

 Chart I have compiled it entirely from my own measure- 

 ments, as no two persons, unless accustomed to work 

 together and check each other's measurements can be 

 depended upon to give exactly the same results in 



