There are many monsters that a glassen surface
Restrains. And none more sinister
Than vision asleep in the eye's tight translucence.
Rarely it seeks now to unloose
Its diamonds. Having divined how drab a prison
The purest mortal tissue is,
Rarely it wakes. Unless, coaxed out by lusters
Extraordinary, like the octopus
From the gloom of its tank half-swimming half-drifting
Toward anything fair, a handkerchief
Or child's face dreaming near the glass, the writher
Advances in a godlike wreath
Of its own wrath. Chilled by such fragile reeling

 The octopus is drifting almost aimlessly in its tank, as subconscious thought is drifting, displaced and floating in the depths of the mind. It approaches ‘anything fair’ attempting to find an opening in the conscious mind that is penetrable. 
 A handkerchief is something extremely delicate and fragile. The apparition searches for a delicate target and finds that in the child’s face.
The Octopus