Answer and Explanation:
This is the way the poem should appear:
Two doves upon the selfsame branch,
Two lilies on a single stem,
Two butterflies upon one flower:--
O happy they who look on them.
Who look upon them hand in hand
Flushed in the rosy summer light;
Who look upon them hand in hand
And never give a thought to night.
A stanza, or a verse, is a group of lines - usually four or more - in a poem. Stanzas are similar to paragraphs in prose. They are separated by a blank line from the following stanza. The poem above has, as we can see, two stanzas.
A line can be defined as a string or sequence of words before a break. The stanzas above each have 4 lines, meaning the poem has 8 lines total.
Therefore, to make it very clear:
How many stanzas does this poem have?
It has two stanzas.
How many lines does this poem have?
The poem has 8 lines.
How many lines are in each stanza?
Each stanza has 4 lines.