Remember that phoronids are known for their beautiful lophophores, the U-shaped crown of tentacles shown below:
While looking at these phoronids, we noticed some of the lophophores looked a little different — some had paired white spots in the center of the lophophore:
Here's a closer look (below). Note that each of the white spots looks like a little bunch of grapes (clusters of smaller rounded blobs). Do you have a guess about what they are?
The next image is the closest I could get with my camera at the time:
Each of the white clusters is a group of small developing embryos. Phoronis vancouverensis is a brooder! The embryos will develop within the lophophore for about 2 weeks. Then the tiny larvae will swim away, spending time in the plankton before returning to the benthos and undergoing metamorphosis into tiny juvenile phoronids.
I felt fortunate to be photographing phoronids on the Fourth of July! :)
P.S. For more information about phoronids, review the post from 27 June 2013.