Of course they can. The process is called Daisy chaining and is part of the firewire specification.
Great. I am only looking to use the chain to mount the disks to my desktop. I think the person I spoke with at Promise support may have thought that I was looking to merge the RAIDs.
Anyhow, I've been using the drives daisy chained for 3 weeks now with no negative results. I think it's going to be ok.