{HEAD ~ a sphering} on {TAIL ~ the fly channel} in fluid communication with the second one of the reagent storage reservoirs; and 
on
{ HEAD ~ a sphering } on { TAIL ~ the fly channel } in fluid communication with the second one of the reagent storage reservoirs ; and
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH