This paper was originally written in 1965. It introduces two principles that determine the derivation of surface structure constituent trees from underlying deep structure trees. The first principle specifies that a non-branching node is eliminated, unless it is a preterminal node directly dominating a lexical item. The second principle is that if the head of a phrase is deleted, the nodes of the phrase dominating the head are eliminated. How to derive reasonable surface trees from underlying trees in a principled manner is much concern in Japanese syntax: due to the agglutinative character of the language under-lyingly complex sentences can become simple sentences at the surface level.