It is rife with witty, obscure conversations like this one, which will make me grin (groan?) for the rest of my life:
SP: We'd better get started. The sponges won't wait, will they, Jim?
JW: No, they get testy.
DS: That's sea urchins who get testy.
SP: Actually, flatworms are the most primitive things that get testes.
I am giggling right now with the memory of it. So awesome. See, urchin skeletons are called tests. And if you're willing to organize animals in a biased way (for the sake of argument) from primitive to advanced and go marching up the ladder, past sponges and jellies, flatworms are the first animal you'll come to that develops true gonads (testes and ovaries).