1903.] IN FANCY MICE AND RATS. 



73 



withstand the ti^eatment moi-e than 24 hours, though ultimately 

 it also (and the keratin) disappeai's. 



The brown may be present in both medulla and cortex ; the 

 black is chiefly deposited in the medulla, but may be cortical also, 

 while it is doubtful whether the yellow is ever present except in 

 the medulla. 



All these pigments may coexist in the same hair ; but hairs are 

 found with only black and brown, others containing only black and 

 yellow. Othei- types possibly occur. The lighter colour is mostly 

 peripheral (in hairs which contain other colours), but brown often 

 is present in the cortex at levels where the medulla contains black. 



In M. sylvaticus the condition is similar, but the amount of 

 black is less. 



The diflerent colour- types of fancy mice are due to the presence 

 or absence of one or more of these pigments in various amounts. 

 Both the yellow and the brown may exist separately, without any 

 other pigment being discoverable, but, so fai-, no mouse has been 

 seen having black only, some brown being always associated with 

 black. 



Each chief type of coloration, black, brown, and j^ellow, exists 

 in at least two forms — the one more intense, the other more 

 dilute. The dilution, which aflfects both medulla and cortex, 

 seems to be due to greater scarcity of the pigment-granules, not to 

 diminution in their size. 



The following list includes all the types examined, though some 

 probably remain to be seen. Waltzing mice, so far, have not been 

 examined. The fanciers' names are generally retained, as on the 

 whole distinctive and practical. Owing, however, to the ambiguity 

 in the use of the term " fawn " to denote both " yellow " and 

 colorations containing other pigments, the term " yellow" is used 

 for the type containing yellow pigment only. 



1. Ordinary Cinnamon {or A gozdi). Yhecolowvoi M.mtiscidibs, 

 having same three pigments. Exists in at least two strains, one 

 rather darker than the other. This is doubtless the " grey " of most 

 writers. Pied forms and strains common. 



2. Golden Agouti. Like (1) but yellower. Contains SrotCT?- and 

 yelloio, without black. 



3. Sahle. This rather striking type is like (1) on the back, but 

 with yellow hairs interspersed at sides. Flanks almost wholly 

 yellow. Pied with white this colour gives the so-called " tricolor." 



4. Blue-and-tan. Not examined microscopically. [Probably 

 sable in which black is diluted.] 



5. Chocolate = Plum. Contains bi-own alone. May be pied. 



6. Silver-faivn. A diluted form of (5). Many hairs have 

 colourless tips. 



7. Yelloio. Contains yellow only. Often called " fawn," though 

 this term is also applied sometimes to colour containing brown or 

 black. When dark pigment is present in association with pre- 

 dominant yellow the colour is spoken of as " dingy " or " sooty 

 fawn." 



