184 CYTOPLASMIC INHERITANCE 
characters are due to peculiarities of the eggs before 
they are laid. 
The serosa on the other hand is a cellular membrane 
that develops around the embryo and produces pig- 
ment. The pigment seen through the shell gives the 
embryo a definite color, which in the hybrid embryo 
is characteristic of the maternal race. Since the 
serosa pigment is not present in the egg, but develops 
after fertilization the inheritance here appears to be 
determined by the character of the egg and not by the 
sperm. But the genetic history of this character of 
the embryo is apparently the same as that of the 
color of the shell or of the yolk.. It can, therefore, be 
interpreted in the same way. There must, then, 
be present in the egg some substance that is at first 
uncolored, and later this substance when carried into 
the serosa produces pigment, presumably by inter- 
acting with something else there. In the next genera- 
tion, however, the influence of the father comes to 
light when the F, embryo produces its serosa mate- 
rial; for now the nucleus of the P, male has had op- 
portunity to determine what this material may be, 
and should the paternal factor be the dominant one 
it determines the kind of material that the eggs will 
contain and hence the color of the serosa of this new 
generation. 
A case of cytoplasmic inheritance has been de- 
scribed by Correns in the four-o’clock, Mirabilis 
jalapa. There is a race whose leaves are checkered 
with green and white, but some branches may have 
leaves entirely green, other branches may have only 
