Yeast Starter Concern

I am planning to brew a Belgian Wit tomorrow. My kit came with a Wyeast propagator smack pack which had me prepare 2 liters of yeast starter. I am fermenting the starter in a tinted growler which is difficult to see into unless I hold it up to the light. I can definitely see a layer of foam on top of the starter and can hear fizzing when I shake it, but I am not able to detect a layer of yeast on the bottom. When I brew tomorrow approximately 40 hours will have passed since I created the starter. Is the layer of yeast on the bottom essential or is my starter showing enough signs of activity (krausen and fizzing) to safely pitch? Thanks.

Abe

Krausen and fizzing are good enough....pitch away, but if it's not settled to the bottom yet, pitch the entire starter - don't try to decant the liquid off the top if you can't see the yeast layer at the bottom.