as Enemies of Maiikind. 



save for the waterside colonies,* continually replenished or re- 

 established by ship rats, B. rattus appears to have become extinct 

 shortly after the middle of the nineteenth century. No doubt the 

 rebuilding of much riparian property, and the gradual substitution of 

 brick and stone buildings for houses of wood, lath, and plaster, 

 throughout the country, have contributed largely to the extermina- 

 tion of B. rattus and to the hindering of its incessant efforts to 

 re-colonize our land. 



In warm countries it has less to fear from the competition of 

 the Brown Eat, and in many, as in India, it remains the dominant 

 species. At sea its superior climbing powers give it a great 

 advantage over the Brown Eat ; it therefore continues to be the 

 principal ship rat. The races frugivorus and alexandrinus form a 

 large percentage of the ocean-going rat population. 



COLOEATION AND HISTOEY OF THE BEOWN EAT, 

 BA TTUS NOB VEGIC US. 



The normal colour of B. norvegicus may be described as 

 follows : — Back greyish, or reddish-brown, heavily " lined " with 

 black hairs along the spine ; belly silvery grey, but in many 

 specimens washed with a dingy yellowish-brown. 



It is of especial interest to note that this species, although first 

 established in Britain within the last two hundred years, is already 

 developing a Black race — described originally from Ireland in 

 1837 as " Mus hibernicus." This black race (frequently confused 

 with B. r. rattus) is becoming commoner and is acquiring a wide 

 distribution. Should it ever become the prevalent form of the 

 species in this country, it would then afford a complete parallel 

 with B. r. rattus, the evolution of which has been described 

 above. 



The tame rats of commerce are apparently all of this species ; 



* One of the best known colonies of R. rattus living in Britain is that 

 discovered at Yarmouth in 1895 by Mr. A. H. Patterson, who has published 

 several accounts of it from time to time. Between 1905 and 1910 these rats 

 increased greatly in numbers and made steady progress through parts of 

 Yarmouth. With reference to this colony, Mr, Patterson, in litt. (April 1918) 

 to Dr. Harmer, states that the species " which is much harassed now is 

 becoming rarer. . . . The war allows no grain ships here, so that the species 

 does not now breed ahead of its destruction. I, however, get three or four 

 dead ones a week." 



