In Kac's classification of finite-dimensional Lie superalgebras, the contragredient ones can be constructed from Dynkin diagrams similar to those of the simple finite-dimensional Lie algebras, but with additional types of nodes. For example, Apn´1, 0q " slp1|nq can be constructed by adding a "gray" node to the Dynkin diagram of An´1 " slpnq, corresponding to an odd null root. The Cartan superalgebras constitute a different class, where the simplest example is W pnq, the derivation algebra of the Grassmann algebra on n generators. Here we present a novel construction of W pnq, from the same Dynkin diagram as Apn´1, 0q, but with additional generators and relations.