Here are the blastula, gastrula and larvae of sand dollars. The cells have divided enough to produce an organism that can exit out of the jelly coat and start swimming around to continue developing. The little parts you see are the ectoderm, mesoderm and endoderm that will develop into muscles, skeleton, organs, etc. I wasn’t able to get a picture of the larval but that drawing is good enough I hope. You can look up all the details on wiki but man, I was so excited about this lab. I think it took about 1-2 days to go from sand dollar zygote to larvae.. and it will take a month until we get baby sand dollars! WOOOO!