The Crustacea may be classified as follows (Claus): A. Entomostraca: small, simply organised; number of somites and of appendages very variable.

1. Phyllopoda: body elongated, generally well segmented, with a shield-shaped or lateral bivalved shell, and at least four pairs of lobed and lamellate natatory feet.

(a) Branchiopoda, which are large sized j with well segmented bodies, and 10-20 or more feet with well-developed branchiae. Branchipus, Artemia, Apus, Limnetis, Limnadia, Estheria.

(0) Cladocera, which are small, laterally compressed with a bivalve shell and large natatory biramose second antennae. Sida, Daphnia, Moina, Bosmina, Polyphemus, Leptodora, etc.

2. Ostracoda: small, with unsegmented body; seven pairs of appendages, and a rudimentary abdomen; all inclosed by a bivalve shell. Cypridina, Cythere, Cypris, etc.

3. Copepoda: elongated; generally segmented; no shell of any kind, and 4-5 pairs of biramose thoracic feet; and five-jointed abdomen. Often parasitic, and then degenerate; e. g. Cyclops, Chondracanthus, Caligus, Lernaea, Argulus, etc.

4. Cirripedia: fixed; body not clearly segmented; inclosed in a fold of the integument, generally strengthened by calcareous valves; as a rule five pairs of biramose thoracic feet; hermaphrodite; e. g. Lepas, Scalpellum, Balanus, Sacculina.

B. Malacostraca. Head composed of five, thorax of eight, and abdomen of six somites.

1 A peculiar Ostracode, Elpidium Bromeliarum, has been found by Fritz Miiller in the water retained by the leaves of Bromeliads in Brazil. It is not found in any of the streams, ponds, etc., around. See Nature, xxii. 1880, p. 55. The Amphipod Phronima makes a 'house' for itself out of a Pyrosoma, a Safya, or even the Siphonophoran Abyla (Mayer, Mitth. Zool. Stat. Naples, i. 1879, p. 46).

1. Leptostraca (=IVebalia): bivalve shell; eight thoracic somites free; abdomen of eight somites, with furcae anales; thoracic limbs Phyllopod-like. Nebalia.

2. Arthrostraca: seven, rarely six free thoracic somites; eyes sessile; no cephalothoracic shield.

(a) Amphipoda: body laterally compressed; branchiae on thoracic limbs; first three pairs of abdominal feet natatory: e. g. Caprella, Cyamus, Talitrus, Or-chestia, Gammarus, Hyperia, Phronima.

(/3) Isopoda: body more or less compressed dorso-ventrally; first pair of abdominal feet form an operculum, covering the other pairs which are branchiate: e. g. Tanais, Anceus, Cymothoe, Anilocra, Serolis, Idotea, Asellus, Bopyrus, Entoniscus, Ligia, Oniscus, Armadillo.

3. Thoracostraca: all or some thoracic somites fused to head; a cephalothoracic shield; eyes mostly stalked.

(a) Cumacea: 4-5 free thoracic somites; two pairs of maxillipeds; abdomen in cT carrying two, three, five pairs of natatory feet; eyes sessile: e. g. Cuma (r=.L)iastylis), etc.

(#) Stomatopoda: short cephalothoracic shield; five pairs of maxillipeds; branchiae on abdominal feet; abdomen large; e.g. Squilla.

(y) Podophthalmata: large cephalothoracic shield; two to three pairs of maxillipeds. (i) Schizopoda: thoracic feet (eight pairs) biramose (Mysis, &c).

(ii) Decapoda: thoracic somites fused to head; five last pairs of thoracic feet uniramose and seven-jointed.

(a) Abdomen long, Macrura; e. g. Lucifer, Sergestes, Penaeus, Palaemon, Craugon, Astacus, Nephrops, Scyllarus, Palinurus, Pagurus, Birgus.

(b) Abdomen short, Brachyura; e.g. Dromia, Maja, Cancer.

See lit. pp. 176-7, 181, 186, 189.

A. Entomostraca, Gerstaecker, Bronn's Class, und Ordn. des Thierreichs,v. Abth. 1. 1866-79, and except Cirripedia, Baird, British Entomostraca, Ray Soc. 1850.

Phyllopoda: Branchiopoda, Packard, 'North American Phyllopoda,' Rep. U. S. Geol. Survey, xii. 1883. Branchipus and Artemia, Claus, Arb. Zool. Inst. Wien, vi. 1886. Limbs of Apus, Ray Lankester, Q. J. M. xxii. 1882; Packard, 'Homologies/ etc. American Naturalist, xvi. 1882. Estheria and Limnadia, Gruber, A. N. 31 (1), 1865. Limnadidae, Klunzinger, Z. W. Z. xiv. 1864.

Cladocera: Polyphemidae, Claus, Dk. Akad. Wien, xxxvii. 1877. Daphnidae, Id. Z. W. Z. xxvii. 1876. New British sp., Ray Lankester, A. N. H. (5), ix. 1882. Lep-todora, Forrest, Journal Roy. Micr. Soc. ii. 1879; Weismann, Z. W. Z. xxiv. 1874.

Ostracoda: Cytheridae, Kaufmann, Recueil Zool. Suisse, hi. (2), 1886. Halocy-pridae, Claus, Schriften Zool. Inhalts. Wien, 1874. Cypridinae, Id. Z. W. Z. xxiii. 1873; Zenker, Monograph, A. N. xx. (I) 1854. Brady, 'Recent British Ostracoda? Tr. L. Soc. xxvi. 1870; Id. Ostracoda, Challenger Reports, i. 1880.

Copepoda: Brady, 'Free and semi-parasitic Copepoda,' 3 vols. Ray Soc. 1878-1880; Id. Copepoda, Challenger Reports, viii. 1883; cf. Baird's British Entomostraca, Ray Soc. 1850. Cyclops, Hartog, J. L. S. xviii. 1885. Development, Urbanovics, Z. A. vii. 1884; and of Cetochilus, Grobben, Arb. Zool. Inst. Wien, iii. 1881. Generative organs of free Copepoda, Gruber, Z. W. Z. xxxii. 1879. Parasitic forms: Chondracanthidae, Vogt, Mem. Inst. Genev. xiii. 1877; Lernaeidae, Claus, Marburg Schriften, Suppl. pt. 2. 1868; Lernaeopodidae, Kurz, Z. W. Z. xxix. 1877; Argulidae, Claus, Z. W. Z. xxv. 1875; Lernanthropus, Heider, Arb. Zool. Inst. Wien, ii. 1879; cf. Z. A. iii.

Cirripedia, Hoek, Challenger Reports, viii. 1883-; x. 1884; Id. Tijdschrift Nederl. Dierk. Vereen, vi. 1882-85. Peltogaster, nervous system, Yves Delage, A. Z. Expt. (2), iv. 1886. Sacculina, Id. op. cit. (2), ii. 1884. Laura Gerardiae, de Lacaze Duthiers, A. Z. Expt. viii. 1879-80 (Mern. Acad. Sciences, Paris, 42, 1883).

B. Malacostraca; see lit. p. 176-77.

Leptostraca; Nebalia, Packard, American Naturalist, xvi. 1882; Claus, Z. W. Z. xxii. 1872; cf. von Willemoes-Suhm, 'Atlantic Crustacea,' Tr. L. S. (2), i. 1870.

Arthrostraca, Gerstaecker, Bronn's Klass. und Ordn. des Thierreichs, v. Abth. ii. 1881-86 (not finished). Caprellidae (Amphipoda\ Mayer, Fauna und Flora des Golfes von Neapel, vi. 1882. Amphipoda of Kiel, Blanc, Nova Acta, 47, 1885. Organismus der Phronimiden, Claus, Arb. Zool. Inst. Wien, ii. 1879. Platy-scelidae, Id. ibid. Amphipoda der Adria, Nebeski, Arb. Zool. Inst. Wien, iii. 1881. Crustacea Isopoda Terrestria, Budde-Lunde, Havniae, 1885. Tanaidae and Apseudes, Claus, Arb. Zool. Inst. Wien, v. 1884. Tanais, Blanc, Recueil Zool. Suisse, i. 1884. Serolis, Beddard, Challenger Reports, xi. 1884. Bopyridae, Waltz, Arb. Zool. Inst. Wien, iv. 1882; Kossmann, Z. W. Z. xxxv. 1881. Entoniscus (Cryptoniscidae), Kossmann, Mitth. Zool. Stat. Naples, iii. 1882; Id. SB. Akad. Berl. 1884. Isopod Anatomy, Huet, Journal de l'Anat. et Physiol, xix. 1883. Cymothoidae, Schibdte and Meinert, Nat. Tidsskrift (3), xii, xiii, xiv.

Thoracostraca. Cumacea: Cuma Rathkii, Burmester, Inaug. Diss. Kiel, 1883; Egg, etc, Blanc, Recueil Zool, Suisse, ii. 1885; Dohrn, 'Bau,' etc. J. Z. v. 1870; Sars, Nye Bidrag til Kundskaben, etc, ii. Middlehavets Cumaceer, Christiana, 1878 (Arch. Math, og Naturvid.); Norman, A. N. H. (5), iii. 1879; Spence Bate, ibid. (2), xvii. 1856. Stomatopoda, Brooks, Challenger Reports, xvi. 1886. Schizopoda, Sars, Challenger Reports, xiii. 1885. Decapoda Macrura: Lucifer, Brooks, Ph. Tr. 173, Pt. I. 1883.

Typical Zoaea, Birge on Panopaeus, Studies Biol. Lab. Johns Hopkins Univ. ii. 1883. Development of some Fresh-water Decapoda: Palaemon potiuna, Fr. Miiller, Z. A. iii. 1880; Palaemonetes, Mayer, Mitth. Zool. Stat. Naples, ii. 1881, p. 197; Atyephira, Ishikawa, Q. J. M. xxv. 1885.

Unicellular cutaneous glands, cf. Claus, Beitrage, etc, Arb. Zool. Inst. Wien, iii. 1881, p. 6; Nebeski 'Amphipoda of Adriatic,' ibid. Antennary glands, Grobben, ibid.

Brain of sessile-eyed Crustacea; comparison of eyed and eyeless fon?is (with lit.), Packard, Mem. U. S. National Acad. Sciences, iii. Eye of Penaeus, etc, Patten, Mitth. Zool. Stat. Naples, vi. 1886, p. 625; of Branchipus, Claus, A. N. H. (5), xviii. 1886; of blind Cambarus, Leydig 'Untersuchungen zur Anat' etc, Bonn, 1883, p. 36.

Lungs of terrestrial Birgus latro, Semper, Z. W. Z. xxx. 1878. Anal respiration, Hartog, Q. J. M. xx. 1880, pp. 244, 485.

Circulation of My sis (Schizopoda), Yves Delage, A. Z. Expt. (2), i. 1883; °f Arthrostraca, Id. ibid. ix. 1881; cf. Claus, cited, p. 181, ante. Heart of Copepoda, Claus, Beitrage, etc. Arb. Zool. Inst. Wien, iii. 1881, p. 2. Blood of Callinectes, Howell, Studies Biol. Lab. Johns Hopkins Univ. iii. 1886.

Urinary organs in Amphipoda, Spencer, Q. J. M. xxv. 1885; in Stomatopoda, Claus, 'Circulation in Stomatopoda) Arb. Zool. Inst. Wien, v. 1884, p. 12.

Sexual organs of $ Cladocera, Weismann, Z. W. Z. xxvii. 1876; xxviii. 1877; o, etc, xxxiii. 1880 (cf. 'Rechtfertigung,' xxx. 1878); of Ostracoda, F. Miiller, Zeit-schrift f. Ges. Natw. (Giebel) 53, 1880; of Cytheridae (Ostracoda), W. Miiller, A. N. 50. (1), 1884; of Oniscidae (Isopoda), Friedrich, Zeitschrift f. Ges. Natw. (Giebel), 56, 1883; of o Decapoda, Brocchi, A. Sc. N. (6), ii. 1875.

Hermaphroditism in Cymothoidae, Mayer, Mitth. Zool. Stat. Naples, i. 1879, p. 165; cf. Nebeski, Beitrage, etc. Arb. Zool. Inst. Wien, iii. 1881, p. 24.

Parthenogenesis in Apus, etc, von Siebold, 'Beitrage zur Parthenogenesis der Arthropoden,' Leipzig, 1871; in Cladocera, Weismann, opp. citt. supra; in Ostracoda, Weismann, Z. A. iii. 1880, and F. Miiller, op. cit. supra.

Changes of colour in adaptation to surroundings, Matzdorff, on Idotea tricuspidata, J. Z. xvi. 1883; Weber, Isopoda Trichoniscida, A. M. A. xix. 1881, p. 591; cf. Seid-litz, 'Beitrage zur Descendenz-Theorie,' Leipzig, 1876, pt. 1; in Nika edulis, Jour-dain, C. R. 87. 1878.

Sexual colours of Daphnidae, Weismann, Z. W. Z. xxx. (Suppl.), 1878.

Parasitism, cf. Kossmann, Z. A. v. 1882, p. 60.

Sexual (male) Polymorphism-, in Amphipoda Chilton, (5), xvi. 1885; cf. Norman, on Eryontidae, A. N. H. (5), iv. 1879. Influence of surrounding media on shape, Schmankewitsch, Z. W. Z. xxix. 1877; cf. Brauer, Z. A. ix. 1886.

Stridulating Crustacea, Wood-Mason, Nature, xviii. 1878; Neptunus vocans, Milne Edwards, Bull. Soc. Philomath, Paris, 1878; Palinurus, T. J. Parker, P. Z. S. 1876.