getting mean values for each raster in a stack

Dear R users

I have a raster stack and a polygon.

I want the mean value inside this polygon for each raster in the stack.

I'm doing the following:

vals <- extract(stack,polygon)
colMeans(r.vals[[1]]) # only for mean values
# or
for (i in 1:nlayers(stack)) {print(mean(vals[[1]][,i]))} # mean or other
parameter

I also tried to use lapply, but I got only the overall mean with
lapply(vals, FUN=mean)

I wonder if there is a way to get the mean (and other parameters) for each
layer using lapply function.

Thanks in advance.

Antonio Olinto