On page 68, Jekyll explains how , when he arrived home , he made a feint of breakfasting. What does this mean? Why did he do this? What does this action show us?

As far as I can tell it means he really just didn't eat much or any breakfast. He explains that upon returning to Jekyll he did not have an appetite. This seems to indicate that his Jekyll self was affected by the physical reminders of Hyde. This shows us that it is increasingly heard to separate the two.