ADAPTATION AND INHERITANCE KAMMEREE. 435 



pie, the ''dark" one. If one produces a second filial generation from 

 a pair of this apparently dark race, {F^), then ''dark" again is domi- 

 nant but only three-fourths, while the remaining fourth is "light" 

 and causes the "light" of the grandparent to reappear. If one 

 breeds from the "light," then "dark" never reappears; the "light" 

 is and remains pure. If one continues to breed the three-quarter 

 "dark" together, then one-fourth continues to breed pure "dark," 

 which always yields " dark " offspring, but the remaining two-fourths, 

 when bred together, yield in the third filial generation (F3), another 

 splitting into three-fourths "dark," of which one-fourth is pure 

 strain "dark" and two-fourths mixed, and one-fourth which is pure 

 "light" strain. This continues as long as the inbreeding permits of 

 the development of offspring. This inheritance scheme, of which 

 our picture cites the simplest possible case, is called Mendel's division 

 scheme or prevalence rule, after its discoverer; that peculiarity which 

 is entirely prevalent in the first generation and three-fourths in those 

 following is called the dominant, and the name recessive is given to 

 that peculiarity which is suppressed entirely in the first generation and 

 reappears in one-fourth of those that follow. The numerical arrange- 

 ment of these peculiarities in the progeny is usually not influenced by 

 the sex of the parent bearing the dominant or recessive properties. 

 This, however, is not true in the case of our crossings in the midwife 

 toad. 



It is true, however, that these experiments fall in line with Men- 

 del's law, but the dominant factor is attached to the male, and a 

 change in dominance depends upon whether we use a male possessing 

 one or another peculiarity. On the other hand, the recessive char- 

 acter in the case of the midwife toad is attached to the female. I 

 feel convinced that this unusual change in the distribution of the 

 habit between the two sexes which we have considered is of impor- 

 tance. But this is secondary compared with the important result 

 that acquired characters not only become transmitted but in the 

 mixing with unchanged characters they follow Mendel's law. The 

 acquired character, therefore, has a chance to come forth pure, in a 

 certain percentage, from the mixture of characters, and is thus pre- 

 served. To this attaches, as we shall learn, a high degree of stability. 

 The new character must have ceased to be a changing or unusual 

 thing; it must have been transmitted to the organism, as we may 

 say, in flesh and blood. 



Next to the midwife toad, the fire salamander {Salamandra Tnacu- 

 losa, figs. 12, 13), which lives in moist woods, has become a favorite 

 of mine. If kept for several years upon yellow clay (fig. 12, P row), 

 then his yellow markings become enriched at the expense of the black 

 ground color. If half of the offspring of individuals which have thus 

 become very yellow (fig. 12, F^ row) be raised on yellow soil, the 



