Theme 'Morphological Classes' Guest Editor: Mark Aronoff.- Syntactically Arbitrary Inflectional Morphology.- Noun Classes in Arapesh.- The Latvian Declension.- Formal Properties of the Conjugations in Modern Aramaic.- The Form Classes of Spanish Substantives.- Morphological Classes and Grammatical Organization.- Theme 'Productivity'.- Quantitative Aspects of Morphological Productivity.- The Relationship between Morphological Productivity and Frequency: A Comment on Baayen's Performance-Oriented Conception of Morphological Productivity.- Constraining Psycholinguistic Models of Morphological Processing and Representation: The Role of Productivity.- Scalar Productivity and -lily Adverbs.- Other Articles.- Morphemic Circumscription.- On the Theoretical Status of Position Class Restrictions on Inflectional Affixes.- Book Reviews.- Renato Oniga,I composti nominali latini: una morfologia generativa.- Yakov Malkiel, Diachronic Problems in Phonosymbolism. Edita and Inedita, 1979-1988.- Book Notices.- Wolfgang U. Dressler, Hans C. Luschutzky, Oskar E. Pfeiffer, and John R. Rennison (eds.), Contemporary Morphology.- Soledad Varela Ortega, Fundamentos de Morfologia.- Journal of the English Linguistic Society, Vol. 7 (1990).- Publications Received.- Notes To Contributors.