Immigration and Innovation?

Before I go single word ahead I would like to tell that I am trying to understand Franz Kafka, and when I was reading a short story of his, this idea of Innovation and Immigration came across my mental screen. There must be some kind of relationship between two, to tell I havent researched about it yet, so this post may seem bit raw. Most of the emmerging economies globally are seeing great deal of migration to their cities from villages, and as it is oftenly cities are seat of innovation. And if we go by nations we can see same in case of US which I suppose sees largest number of immigrants and is one of the biggest innovator and inspite of doldrums it will come up without major problems( at least we can hope for that).
I am at present wondering what can be the relationship between two, what all can be the postulates to come on some generalised solution to my question. If we look deep into any such relationship then we will aslo have to see into the numbers and figures. See there is Japan and Germany few of the top most economies and they do not boast of high number of immigrants and still they are good on innovation list...so I have to figure it out.