The speaker imagines that a hard knock to the head let his dreams spill out of him, and then describes them as if they were living creatures. They are jelly-like and see-through, pale reds, blues and greens, a bit like deep-sea animals that rarely meet the light. He can only catch them from the corner of his eye, so they stay just out of clear view. There are only about half a dozen, and the speaker isn't even sure of the number, which makes the memory feel loose and dreamlike.
The tone is odd, quiet and a little funny. The speaker talks about something impossible in a flat, matter-of-fact voice. Then the poem turns: if he lets life "slow or backslide," the dreams get agitated. They seem to want him to keep moving, to chase what he cares about. The final image, a dream kicking him in the shin, is both comic and a bit of a scolding. The mood is playful, but underneath it carries a gentle worry about neglecting your own hopes.