@Chet31
I was about to write a response about Darwin, but see that toriaezu wrote an excellent one already. I'll just expand further.
In Darwin's time there was no agreed-upon model of heredity; in Chapter I of
Origin of Species, Darwin admitted, "The laws governing inheritance are quite unknown." Darwin accepted a version of the inheritance of acquired characteristics (which after Darwin's death came to be called
Lamarckism) as toriazu noted.
Darwin wrote a second book in 1868 called
The Variation of Animals and Plants under Domestication, which tried to explain heredity through his hypothesis of
pangenesis. Although Darwin had privately questioned blending inheritance, he struggled with the theoretical difficulty that novel individual variations would tend to blend into a population. However, inherited variation could be seen.
It was not until the modern evolutionary synthesis in the 1930s and 1940s that a model of heredity became completely integrated with a model of variation.
You can't blame Maries for a lack of familiarity with concepts that would not be fully understood for another 50 years.