The phrase 'Like a Lamb to the slaughter' suggests that the slugs are patiently waiting for death. A lamb would not know that they are being led to death, all they see is bait, and they are content.
Like lambs to a slaughter suggests that the slugs (much like the sheep) have no idea that death comes soon, for the slugs either the birds will get them, they get dried out(?), or they risk being found by a human. For the sheep, they’re happy because they have an unlimited supply of food and they’re happy, but they’re being led to their deaths.
Peter and Anne fell in love. They cuddled and kissed in Peter's room and in the attic. But after a while Anne realised that Peter would never become the friend she had hoped for. She backed off a little, but Peter did not.
