Polyprefixation and its consequences (Notes on the physiology of the Russian verb).

The article offers a theory accounting for the internal structure of a verb stem in Russian and, specifically. for constraints on multiple prcfixation. The theory consists of two components. The first component relies on the hypothesis, independently motivated in the literature, that verbal prefixes fall into two types, lexical (internal) and superlcxical (external). The second component is a novel hypothesis that the group of external prefixes is not homogeneous: some of them observe a selcctional restriction, others are positionally restricted. The selcctional restriction says that a stem to which a prefix attaches must be formally imperfective. The positional restriction bans a prefix merging on top of the so called secondary imperfective morpheme. The main focus of the article is to explore the predictions the theory makes with respect to the derivational potential of a verb stem, namely, its ability to undergo imperfec-tivization, adjectivization and nominalization.