An Index of the Rotifers in the C. B. Morris Collection of Microscope Slides at the Cawthron Institute, Nelson By C. R. Russell [Read before the Canterbury Branch, February 13, 1950; received by Editor, February 20, 1950.] The changes made in recent years in the classification of the Rotatoria have increased the value of slides mounted by early workers, and without them it would sometimes be impossible to determine the species which have been described. Individual slides of rotifers may be found in many private and institutional collections throughout the Dominion, but the existence of a systematic collection was unknown to the author until Mr. A. W. Parrott, Curator of Insects at the Cawthron Institute, forwarded a box of sixty-three slides collected by the late Mr. C. B. Morris, of Oamaru, with a request that they be indexed and treated for leakage. Mr. Morris published two papers: “Some Notes on Rotifers, not previously described in New Zealand,” 1912, Trans. N.Z. Inst., vol. 45, pp. 163–7, and “A Classified List of the Rotatoria of New Zealand,” 1913, Trans. N.Z. Inst., vol. 46, pp. 213–9. The 1913 list did not, however, include the collection of Murray (1911) published two years earlier. Apparently the new material included in the above papers was based on the collection now at the Cawthron Institute. All the slides employed formalin-water media, and as a rule such slides have only a short life; it says much for the skill of the mounter that after nearly forty years thirty-seven of the slides are still in perfect condition. The procedure adopted after consultation with Mr. Parrott was to remove the faulty slides from which the media had evaporated. The remaining slides were then ringed with two coats of Murrayite and one of synthetic enamel. The identification of the animals was checked, and a new number given to each slide. The names on the labels were in many cases those in use prior to the paper by Harring (1913) which are now invalid or synonyms, and these were not altered; the correct specific name is given in the Index against the slide number. In only one case was the identification of a specimen found to be incorrect. In two cases which are noted in the Index specimens were removed from leaking slides and mounted in glycerine jelly. My thanks are due to Mr. Parrott and the Cawthron Institute for permission to examine and index this interesting collection, which will probably prove to be the only systematic assemblage of Rotatorian slides in the Dominion. Index Slide Number Name Genus Trichocerca 1,2 T. longiseta (Schrank) 3 T. rattus (Muller)