(ii.) Lateral extension of the epidermis not so conspicuous, and the cells composing it smaller. Tactile organs in little depressions. Transverse as well as longitudinal muscles in the trunk. Adhesive cells on the ventral surface of the body. No interval between the lateral fins and the tail fin. Two papillae on the head-hood elongated into club-shaped tentacles. Hooks 8-9, slightly serrated; anterior spines 3-4; posterior spines 3-4.—SPADELLA CEPHALOPTERA. (iii.) Similar to the last-mentioned species, but the tail segment is larger than the trunk; in the above it is of the same size. No adhesive cells. The fins are covered with papillae, and with a number of serrated spines pointed at both ends.—SPADELLA PONTICA. (iv.) Tactile organs and adhesive cells are unmodified epidermal cells. Anus dorsal. Orifice of oviducts ventral. No olfactory organ. Epidermis colourless. Lateral fins without rays. A pair of ganglia at the postero-lateral angle of the brain.—SPADELLA MARIONI. (v.) Tactile organs well developed on the head, trunk, and fins; tail segment a little shorter than the trunk. Body short, length 3-4 mm. Hooks 9; anterior spines 4-5, posterior spines 6-7.—SPADELLA VOUGAI. ROTIFERA, GASTROTRICHA, AND KINORHYNCHA BY MARCUS HARTOG, M.A., Trinity College (D.Sc. Lond.) Professor of Natural History in the Queen's College, Cork. {197}CHAPTER VIII ROTIFERA, GASTROTRICHA, AND KINORHYNCHA ROTIFERA—HISTORY—EXTERNAL FEATURES—MOVEMENT—ANATOMY—REPRODUCTION— EMBRYOLOGY—CLASSIFICATION—DISTRIBUTION—AFFINITIES—GASTROTRICHA— KINORHYNCHA The Rotifera are microscopic animals, the largest not exceeding one-eighth of an inch in length. According to Hudson and Gosse,[233] they are first recorded in an observation of the Rev. John Harris, in 1696, of "an Animal like a large Maggot which could contract itself into a Spherical Figure, and then stretch itself out again; the end of its Tail appeared with a _Forceps_ like that of an _Ear-wig_."[234] This was certainly a Bdelloid Rotifer.