Secondly, there are those variations which occur in Zygotes of similar germinal constitution and which are caused solely by differences in the environment to which the individuals are respectively exposed: these are the "acquired characters" of Lamarck and of authors generally.
"Darwin and Modern Science"
A.C. Seward and Others
On fertilisation two kinds of Zygotes are formed, female-producing eggs with 2N chromosomes, and male-producing eggs with 2N-1 or 2N-2 chromosomes.
"Hormones and Heredity"
J. T. Cunningham
My conclusion from the evidence is that any process of congenital development may in particular Zygotes exhibit a mutation, a departure from the normal.
"Hormones and Heredity"
J. T. Cunningham