Sleep tight, little cleavage stage,
In your fertilization envelope.
You can rest while I draw this page;
You’re safe under my microscope.
Sleep tight, little blastula,
While your cilia take you for a ride.
Soon you’ll be a gastrula;
Meanwhile, snuggle on my cover slide.
Sleep tight, little larval form,
Pluteus, ancestrula*, or trochophore.
The lab won’t let you get too warm,
And the plumbing drains right to the shore.
* After following the link, hit ctrl-F and type "ancestrula".