Bitterness.

The poem Untitled by Stephen Crane had a very dismembered meaning behind it. This poem was not read to be analyzed as literal, meaning that the "being" is not actually eating his REAL heart but rather looking inside the soul. The author looks at this creature amidst the desert, and many times the desert (as in the bible) is looked upon a place that ceases to have hope...the bitterness would be easy to gain insuch a desolate place. The creature that the author is looking at is holding his heart.
HOLDING HIS HEART.
 Automatically the human reaction is disgust, repulse, and even pity. As we look further into the "holding" of his heart and ultimately eating it that is the refelction of human kind on their character and what may be held deep inside the heart.
"I said: 'Is it good, friend?"'
This line is the potential we have as humans to pass by the anguish of another, many times we would rather ignore the helpless than help them get through the day. The answer of the "creature" is simple, "It is bitter..".
Poems are meant to be symbols, and this line is a deep reflection of what the human character has to reside to when they have seen no love. No love causes us to grow bitter, and see ourselves as though creatures growing bitter against everything throughout the world.
The structure of the poem is simple and short, it requires no further explination of the story. Along with the title of the poem being "Untitled" could go from the story being untitled.. or even the creature. The creature being unknown, unloved-and further- untitled.