112 INHERITANCE IN GUINEA-PIGS. 



This explanation fits very well the results which have been given 

 qualitatively. As the numbers are rather small, and as it is necessary 

 besides to assume some overlapping of class ranges, much emphasis 

 can not be laid on the quantitative results. Nevertheless, the fit is 

 in all cases reasonably close. Let us take up the qualitative results in 

 order. 



(1) In some stocks there is very little variation in the rough char- 

 acter and there is a wide gap between the lowest rough and smooth. 

 Evidently if the 4-toe and similar stocks are pure for factor s, only 

 full-roughs and smooths can appear (RRss, Rrss, rrss). Apparently 

 7 of the original 8 in the Lima stock were ss, while one, L6, was rrSs. 



(2) When a wild species of cavy (smooth) or a smooth of certain tame 

 stocks is crossed with a full-rough, the rough young are of low grade, 

 rough C or D. This result necessarily follows from a cross of the type 

 rrSS (wild, lea, tricolor) by Rrss (rough A). The rough young RrSs 

 should be rough C or D. 



(3) When a wild cavy is crossed with a partial-rough guinea-pig, 

 rough young of the lowest grade, rough E, are produced. 



rrSS X RrSs = RrSs + RrSS + 2rr 

 Sm C C E 2Sm 



(4) Partial-roughs crossed together may give all grades of roughness 

 from full-rough (A) to the lowest partial-rough (E). Most of the 

 partial-roughs handled should be RrSs. 



RrSs X RrSs = 3 Rss + 6 RSs + 3 RSS + 4 rr 

 C C 3A 6 C, D 3 E 4Sm 



(5) Full-roughs crossed together have never given partial-roughs. 

 A full-rough, whatever its parentage, must be RRss or Rrss. There is 

 no way in which factor S, necessary for partial-roughs, can be trans- 

 mitted by full-roughs. 



(6) Full-roughs, one or both of whose parents were partial-roughs, 

 have given no partial-rough young on crossing with smooths of 4-toe 

 stock. Smooths of 4-toe stock are all necessarily rrss and can not 

 transmit factor S. 



(7) Partial-roughs crossed with smooths of 4-toe or a similar stock 

 give partial-rough young and also, in most cases, full-rough and smooth 

 young. 



RrSs X rrss = Rrss + RrSs + 2 rr 



C Sm (4-toe) A C 2 Sm 



(8) Most partial-roughs crossed with full-roughs^give a very similar 

 result to the cross partial-rough by 4-toe smooth,* except that fewer 

 smooths are produced. 



RrSs X Rrss = 3 Rss + 3 RSs + 2 rr 

 C A 3A 3C 2Sm 



(9) The lowest grade of roughs (E) very rarely have^ either a full- 

 rough parent or full-rough young. They also very rarely have a 



