When I took this picture, the embryos were still developing inside the capsules. A few days later, some of the larvae emerged from the capsules as active swimming veligers.
These Janthina larvae are extremely small, and are good swimmers. Here are two still shots (the best I could manage), but at the end of this post there's a short video clip that's much better.
View from the side:
View from above:
Mostly what you're seeing is the reddish shell and the ciliated velar lobes. In the video, watch for the long cilia beating along the edges of the velar lobes — the motion is useful for both swimming and feeding.
Note that this video was made under a microscope — it's magnified 200x!
By the way, from what we can gather, not many people have filmed Janthina larvae, so although this is a short video, you're probably one of the few people in the world to watch a swimming Purple Sea Snail veliger!
[If you're receiving this via e-mail, click on the title of the video below to watch the clip.]