Chlamys

The embryos of the scallop Chlamys form lovely polar bodies and a polar lobe almost as big as the daughter blastomeres. After that they are sort of hard to take a picture of; until the larva is fairly advanced, the muddy-colored yolk makes it hard to see anything inside. The larva has a bivalve shell and a proportionately large velum with long cilia that make it rather hard to catch!

These scallops are easy to sex just by looking in the shell; they have large gonads that are swollen when ripe, bright orange for females and white for males. When ripe they spawn enormous numbers of gametes within hours after injection of serotonin into the muscle. The eggs seem to lack any investing coats, except that some sort of jelly layer is visible around zygotes and cleavage stage embryos.