Forams

The case of the three species of protozoan (I forget the names) which apparently select differently sized grains of sand, etc., is almost the most wonderful fact I ever heard of. One cannot believe that they have mental power enough to do so, and how any structure or kind of viscidity can lead to this result passes all understanding.

-- Charles Darwin, letter to W.B. Carpenter, 1872, quoted at Bowserlab

Foram shells are formed from a number of different materials; sand grains, calcium, sponge spicules and other foram shells are base essentials. Certain species – Astrammina rara, for example – demonstrate a deliberate (and quite staggering, I think) process of selection. They repeatedly select opaque sediment grains of a consistent shape and size, which they proceed to glue together to form a tight sphere. They complete their elegant structure with the addition of one larger red stone. Why is this? How do they differentiate scale and colour? Is it possible that uni-cellular organisms possess intelligence? A sense of aesthetic?

-- Claire Benyon (2009)