Fréchet spaces with no infinite-dimensional Banach quotients

We exhibit examples of Fréchet Montel spaces E which have a non-reflexive Fréchet quotient but such that every Banach quotient is finite-dimensional. The construction uses a method developed by Albanese and Moscatelli and requires new ingredients. Some of the main steps in the proof are presented in Section 2. They are of independent interest and show for example that the canonical inclusion between James spaces J p ⊂ J q , 1 < p < q < ∞ , is strictly cosingular. This result requires a careful analysis of the block basic sequences of the canonical basis of the dual J p ′ of the James space J p , and permits us to show that the Fréchet space J p + = ⋂ q > p J q has no infinite-dimensional Banach quotients. Plichko and Maslyuchenko had proved that it has no infinite-dimensional Banach subspaces.