The poetical forms in The Nights are as follows:—The Misrá’ah or hemistich is half the “Bayt” which, for want of a better word I have rendered couplet: this, however, though formally separated in MSS. is looked upon as one line, one verse; hence a word can be divided, the former part pertaining to the first and the latter to the second moiety of the distich. As the Arabs ignore blank verse, when we come upon a rhymeless couplet we know that it is an extract from a longer composition in monorhyme. The Kit’ah is a fragment, either an occasional piece or more frequently a portion of a Ghazal (ode) or Kasídah (elegy), other than the Matlá, the initial Bayt with rhyming distichs. The Ghazal and Kasídah differ mainly in length: the former is popularly limited to eighteen couplets: the latter begins at fifteen and is of indefinite number. Both are built upon monorhyme, which appears twice in the first couplet and ends all the others, _e.g._, aa + ba + ca, etc.; nor may the same assonance be repeated, unless at least seven couplets intervene. In the best poets, as in the old classic verse of France, the sense must be completed in one couplet and not run on to a second; and, as the parts cohere very loosely, separate quotation can generally be made without injuring their proper effect. A favourite form is the Rubá’í or quatrain, made familiar to English ears by Mr. Fitzgerald’s masterly adaptation of Omar-i-Khayyám: the movement is generally aa + ba; but it also appears as ab + cb, in which case it is a Kit’ah or fragment. The Murabbá, tetrastichs or four-fold song, occurs once only in The Nights (vol. i. 98); it is a succession of double Bayts or of four-lined stanzas rhyming aa + bc + dc + ec: in strict form the first three hemistichs rhyme with one another only, independently of the rest of the poem, and the fourth with that of every other stanza, _e.g._, aa + ab + cb + db. The Mukhammas, cinquains or pentastichs (Night cmlxiv.), represents a stanza of two distichs and a hemistich in monorhyme, the fifth line being the “bob” or burden: each succeeding stanza affects a new rhyme, except in the fifth line, _e.g._, aaaab + ccccb + ddddb and so forth. The Muwwál is a simple popular song in four to six lines; specimens of it are given in the Egyptian grammar of my friend the late Dr. Wilhelm Spitta.[444] The Muwashshah, or ornamented verse, has two main divisions: one applies to our acrostics in which the initials form a word or words; the other is a kind of Musaddas, or sex-tines, which occurs once only in The Nights (cmlxxxvii.) It consists of three couplets or six-line strophes: all the hemistichs of the first are in monorhyme; in the second and following stanzas the three first hemistichs take a new rhyme, but the fourth resumes the assonance of the first set and is followed by the third couplet of No. 1, serving as bob or refrain, _e.g._, aaaaaa + bbbaaa + cccaaa and so forth. It is the most complicated of all the measures and is held to be of Morisco or Hispano-Moorish origin.