COLOR AND COAT CHARACTERS. 25 



by the sperm of the wild male, upon entering the egg of a tame female, 

 should show many strange and unaccustomed reactions, disturbances, 

 and possibly modifications. No one was surprised that Hertwig (1910) 

 could cause crippled embryos to appear by treating frogs' eggs with 

 radium raj^s, and no one need postulate that such treatment eliminated 

 some of the genes necessary to the normal development of certain 

 organs. And so, the series of reactions which take place in a fairly 

 stereotyped manner, when wild agouti develops in the pure wild race, 

 may well be upset when one or several materials, necessary for this 

 series of reactions, are carried by the wild sperm to such an unaccus- 

 tomed environment as the egg of another species. This modification 

 of agouti does not vitiate the Mendelizing inheritance shown in tables 

 6 to 11, for the material body which carries the agouti factor originally 

 contributed by the wild sperm separates from its homologue, contrib- 

 uted by the egg. The material bodies or carriers (possibly chromo- 

 somes) separate. The activator of the rhythmic deposition of pigment 

 in the hair, the agouti factor, residing in one of these carriers may have 

 been modified or unmodified; yet, modified or unmodified, it separated 

 from its allelomorph. 



Summarizing the facts observed : 



(1) Each f wild hybrid received a single dose of agouti from a wild 

 male; 11 of the 14 | wild were dark with ticked bellies, and varied 

 from forms much darker than the wdld to forms like the darkest wild. 



(2) This modification shown by some | wild females was present in 

 their offspring for the next successive six generations. In some cases 

 the agouti gradually became darker, but in others the change took 

 place more quickly. 



(3) The modification shown by other ^ wild females did not persist 

 in all cases, for they produced light individuals as well as very dark 

 ones. When light i or | wild forms were thus produced, these gave rise 

 either to very dark forms again or to light forms. When dark J wild 

 were produced they also gave dark and light offspring. 



Disturbances which quite baffle the cut and dried Mendelian inter- 

 pretation are not unknown in wide crosses. Not only do we find meta- 

 bolic disturbances, as in the echinoderms and insects, but in cases where 

 adults have been raised there often occur gynandromorphs, hermaph- 

 rodites, and the like (Standfuss, 1895). Up to the present time the 

 mitoses of the hybrid germ-cells in these crosses have not been given the 

 study which they deserve, and consequently an intimate acquaintance 

 with internal mitotic phenomena of hybrids has not been formed. 



Modified Wild Agouti in Crosses. 



Irrespective of the uncertain manner in which the agouti character 

 expressed itself in the first three hybrid generations, there were some 

 families which consistently gave dark forms for a number of generations. 



