ALBINOS 11 



In the present connection our interest in the Norway rat is 

 due mainly to the fact that the common albino rat (M. n. albi- 

 nus) kept as a pet or laboratory animal, and concerning which 

 we desire all possible information, is a variety of the Norway 

 rat. This relationship is shown not only by the usual methods 

 of comparison, but also by the haemoglobin crystals (Reichert 

 and Brown, '09) the shape of skull (Hatai, '07 c) and the fact 

 that the two forms interbreed freely. 



Concerning the place and time of origin of the albino strain 

 there is little information at hand. Allusions to albino rats be- 

 fore the time when the Norway rat appeared in Europe clearly 

 show that there must have been an albino strain of Mus rattus. 

 What we know of the present distribution of Albinos of Mus 

 rattus has been given on pages 5 and 6 in the preceding chapter. 



By sonie curious slip however, many of the natural histories 

 and books of reference speak of the common Albino as an Al- 

 bino of Mus rattus. This of course is not correct, but owing 

 to the confusion thus early introduced, it is difficult to trace the 

 history of the present albino variety^ of the Norway. 



We do not know whether the common albino variety had a 

 single or multiple origin, or whether the colonies found in Europe 

 (Rodwell, 1858) are directly related to those now existing here. 

 Moss, 1836, mentions Albinos in or near Bristol, England about 

 1822. Judging from thje way in which the Albinos of other 

 species arise, we may safely assume that the present strain is 

 derived from one or more albino mutants or sports (Hatai, '12). 

 These must have been captured and the albino descendents 

 segregated and kept as pets, as at present*^ there is nowhere to 



^ Unfortunately there is one more complicating circumstance — namely, the 

 existence of a melanic variety of Mus norvegicus. This melanic variety is often 

 mistaken for Mus rattus rattus because of its color, and this leads to errors of 

 statement concerning the distribution of Mus rattus and also concerning the 

 ability of the two species— rattus and norvegicus — to interbreed. They are in 

 fact mutually infertile (Morgan, '09) (The Hagedoorns, '17). The number of 

 incidental allusions to this melanic variety of norvegicus shows its occurrence to 

 be widespread. See: Edwards, 1871, 1872. Hamy, '06. I'lsle, 1865. Lapicque 

 and Legendre, '11. Schaff, 1891. Webster, 1892. 



^ Rodwell, 1858, page 10, mentions what may have been a colony of Albinos 

 living wild at the Ainsworth Colliery near Bury, England. 



