… sea biscuits, that is – what we call sand dollars. PZ has just posted a video clip of the early development of sand dollars, & it’s absolutely gorgeous. It starts, as he says, with a bit of echinoderm porn – I never knew that sand dollar sperm looks like that whipped ‘cream’ stuff that come out of a pressurised can! And then you get to see fertilisation, cleavage, the early larval stages – which baby sand dollars spend, like all other echinoderm larvae, as plankton – and metamorphosis into this gorgeous little juvenile. Which is tiny – the clip shows it moving about (on its little tube feet) among individual sand grains. Quite lovely.