Botryllus, a fairly non-descriptive name, probably just some tiny organism that is not worth looking for. The first time I found one I could not even start to understand what it was, I struggled to even define it as a plant or an animal. Flowers under water?
The next stone revealed a different colour, then another and so it went on. Not only had I found something new I seemed to find multiple species of it. Take a buttercup bleach it white, cover it with a thin jelly-like substance and let the kids out with a colouring kit. The end result is one single species, a star ascidian in fantastic colour forms. There seems to be absolutely no reason whatsoever for it to be so varied in colour, other than to make photographers spend half an hour trying to get the best shot.
What is a star ascidian? It is a colonial thing, a creature that has an intake opening and a shared waste opening. This is then covered in a test, a jelly. I say a thing because I still do not know what makes this an animal. This is Botryllus schlosseri, once you find it you will keep looking for more. Look under stones on the lower shore.
So now you are under a big rock, looking at a pretty jelly flower, next to it is another tiny bit of jelly, this time a blob, you press it and water squirts out. It looks like a baked bean, you look further under the rock and there are hundreds of them. When you crawl out you find different jelly on plants, on rocks everywhere, welcome to the world of sea squirts (Ascidians). These impossible to identify organisms (well a few like Botryllus are easy) will keep you amused for hours. You go home with endless pictures absolutely sure you will find it in the book and… you will discover a vast array of blobs exist and realise you have been seeing them but not realising they were even creatures.
The basic body design is one tube in one out, they filter water for small particles. These are trapped in mucus and passed to the oesophagus by tiny hairs (cilia). In colonial forms, the exhalent siphon is often shared by the group. Ascidians have a free swimming form in reproduction, this resembles a tiny tadpole, it has a notochord in the tail, a primitive form of backbone. This means they are chordates just like us. Try and get the blob-like forms under water, when they are high and dry they contract and are even more impossible to identify.