bered. They are arranged in two great divisions, depending on the absence or presence of small foramina in the shell wall, viz., imperforata and perforata. The great chalk cliffs of the south of England are almost entirely composed of microscopic shells of this order, while the stone of which Paris is built is mainly composed of the shells of these animals. IV. AMÆBEA (άuoißâios, interchanging).—This order is so named in consequence of its members constantly changing their shape; they are all minute aquatic animals. Their body is composed of a simple sarcode substance, containing a nucleus and contractile vesicle, and has the power of throwing out pseudo-podia that are generally blunt. 2. GREGARINIDE (gregarius, occurring in numbers) are minute unicellular animals, living as parasites in the alimentary canal of vertebrate and invertebrate animals, and frequently found in the intestines of the cockroach and earthworm. The body consists of a single cell, containing granules of sarcode, a nucleus and nucleolus, and does not possess the property of emitting pseudo-podia. FINIS. APPENDIX. HUMAN PARASITES. The best and most concise description of the parasites that infest the human subject, that I am aware of, is to be found in Dr. Aitken's celebrated Practice of Medicine, from which I have copied the following tabulated arrangement of the Entozoa, and where full information on this interesting subject can be obtained. ENTOZOA. "A. SOLID WORMS-PLATYLMIA; vel, STERELMINTHA. I. CESTOIDEA-Banded, riband-like, girdled, or tape-worms, in the form of 1. Mature sexual parasites, androgynous, and living in the alimentary canal. (a.) Tania. 1. Taenia solium (LINNEUS), the common tape worm of man in this country. mediocanellata (KUCHENMEISTER), the common tape-worm of man on the Continent. marginata (BATSCH, COBBOLD). elliptica (BATSCH, COBBOLD). 5. Tania acanthotrias (WEINLAND, COBBOLD), its larva, scolex, or cysticercus only 6. 7. 8. known. nana (SIEBOLD), a very small filiform Tania. flavopunctata (WEINLAND, COBBOLD). echinococcus (SIEBOLD). (b.) Bothriocephali. 1. Bothriocephalus latus (BRemser); vel, T. lata (LINNAEUS), the broad tapeworm, endemic to man in some localities only. Its embryo is ciliated and developed in water (KNOCH). 2. Bothriocephalus cordatus (LEUCKART), new to science; recently found in North Greenland. 2. Immature non-sexual, cystic, or vesicular parasites, the embryonic form of the genera sub (a.) Tœniæ. (a.) Cysticerci. 1. Cysticercus tæniæ cellulosa (RUDOLPHI), the larva or scolex of the T. solium. |