The early development of multiple sense types for the English prepositions 'in, on, at, to, for, from, with, by', and 'of' has been charted on the basis of longitudinal data obtained from the CHILDES corpus for two English-speaking children. In Cognitive Linguistics, prepositions are assumed to be complex lexical categories each associated with a range of polysemous senses. This set of prepositions was selected on the basis of differences in the concreteness of their locative meaning, their varying semantic transparency across a range of sense types, their differing grammatical function, pragmatic relevance, frequency of occurrence, and overall shared monosyllabic shape. While inter-prepositional correspondences and discrepancies are of some interest, the discussion focuses on intra-prepositional commonalities and differences between these two children and addresses implications findings like these have for researchers in cognitive lexical semantics. Even a broad picture such as this of the progress of lexical acquisition by two children calls into question the applicability of certain cognitive mechanisms such as metaphor, metonymy, and schematization deemed to be responsible for the (uni-directionality of semantic extension observed historically. These mechanisms, while not claimed to be teleological, can take a linguistic form with a concrete lexical meaning and eventually render it reduced, abstract, and highly grammaticalized in function. Such mechanisms are also assumed to have motivated lexical organization synchronically, i.e., in the adult speaker's mental lexicon (as given in lexical network models in Cognitive Linguistics). However, the data presented here suggest that each child seems to have his or her own starting point within a lexical category - one which may not be conceptually basic - with additional senses appearing in a piecemeal fashion, usually as part of a favorite fixed expression, rather than through stepwise semantic extension driven by processes such as metaphor and schematization. (Sally Rice)