Persona is how someone acts around a certain social group and shadow is a inward personality that is usually hidden and not fully conscious.
In this novel Dr.Jekyll has a persona of being respectable and not a threat. Mr.Hyde has a persona of being rude and evil. For example, on page 4 Mr.Hyde tramples a 8 year old girl and has no remorse about it.
I also feel as if Mr.Hyde is both a persona and shadow that Dr.Jekyll hides behind. Dr.Jeykll has this evil shadow that transforms into Mr.Hyde so that he can be that side of himself that he hides away. He might of wanted to create Mr.Hye so he could have