CLASSIFICATION 7 



It has been found however in arranging the literature that it 

 would prove most useful to include in Part I all of the incidental 

 and general observations on the wild Norway, on the ground 

 that these applied to the entire species, and to reserve for Part 

 II the more precise data which apply to the wild Norway, as 

 contrasted with the domesticated Albino. 



The reader therefore will find in the literature cited in Part 

 I papers referring to M. decumanus, M. norvegicus and Epimys 

 norvegicus as well as to the Albino (M. norvegicus albinus or 

 var. Albino), sometimes designated the 'white' rat. 



As will be pointed out in the section on The Early History 

 of the rat, there is one more complication in this connection. 

 Through an error, unfortunately perpetuated by some of the 

 natural histories, the common Albino has been described as an 

 Albino of the house rat — Mus rattus. 



It thus happens that in some of the papers cited it is reported 

 that the observations had been made on Mus rattus or ratus 

 (sic), the word albino being sometimes added — sometimes 

 omitted. In a few instances it is impossible to determine whether 

 M. rattus is used for the Albino or whether the house rat was 

 really studied. 



In forming a judgment on these cases it must be kept in mind 

 that for the last half century the house rat has been rare and 

 hard to obtain both in western Europe and in the northern 

 United States, so that unless the author gives good evidence for 

 the name he has employed, it becomes highly probable that he 

 was working with some form of the Norway. For these reasons 

 it has been found most convenient to include also in Part I all 

 the references to the house rat (Mus rattus). 



CLASSIFICATION AND NOMENCLATURE OF THE COMMON RATS 



Up to 1881 Mus (Linnaeus, 1758) was used as the generic des- 

 ignation for both the rats and mice. In 1881 Trouessart pro- 

 posed the subgenus Epimys for the larger forms, the rats, reserv- 

 ing Mus for the smaller forms, the mice — Mus musculus being 

 the type. In 1910 Miller established the use of Epimys for the 

 rats and the change has been accepted. 



