To hear for their tiny hearties

There are many suggestions in this chapter and elsewhere in FW that HCE's sleep / death / internment is also an incubation in the womb of ALP as an egg (Humpty Dumpty) in "foetal sleep" awaiting (re)birth / resurrection. Such a reading of this paragraph suggests ALP moves in "arundgirond in a waveney lyne" - circulating like a line of blood, like "Santa Claus" (dressed in red and bringing "birthday" presents - of oxygen and nutrition), "encircling" (like a womb) her children Isolabella, "then running" (like blood) to the twins "Romas and Reims".

Words here like "spatters" also suggest blood.

"Christmas" also refers of course to the birth of Christ.