$171. THE ACEPHALA. 187 
Vogt. Anatomie der Lingula anatina. Ibid. VII. 1843, p. 1, Taf. I. IT. 
Van Beneden. Mémoire sur ’Kmbryogénie, l'Anatomie et la Physiologie 
ee cae simples, &c., in the Bullet. de l’Acad. royale de Belgique, 
- No. 2. 
ADDITIONAL BIBLIOGRAPHY. 
Kolliker. Ueber das Vorkom. d. Holzfas. im Thierreich., in the Ann. d. 
Sc. Nat. 1846, p. 198, Pl. V.-VII. 
Van Beneden. Recherches sur lEmbryogénie, |’Anatomie, et la Physi- 
hg des Ascidies simples, in the Mém. de Acad. Roy. de Belgique, XX. 
Frey and Leuckart. Beitragen zur Kenntniss der wirbellosen Thiere 
mit besonderer Berucksichtigung der Fauna des Norddentschen Meeres. 
Braunschweig, 1847, p..46, Anatomie des Pfahlwurmes (Teredo navalis). 
Deshayes. Exploration scientifique de lAlgérie, pendant les années 
1840, 1841, 1842. Histoire naturelle des Mollusques, avec un Atlas de 
117 Planches. Paris, 1847. 
Ed. Forbes and Hanley. A History of British Mollusca and their 
Shells. 4 vol. London, 1853. [Contains many anatomical details.] 
Dalyell, T. G. Rare and remarkable animals of Scotland, represented 
from living subjects, with practical observations on their nature. Vol. II. 
London, 1848, p. 138-173, Pl. XXXIV.—XLIIL. (Ascidiae). 
Lovén. Om utvecklingen af Mollusca acephala, Oversigt af k. Vet. 
Akad. Forhandl. 5te Argangen, Dec. 1848, Stockholm, 1849, p. 233-257 ; 
or, its translation in Madler’s Arch. 1848, p. 531; or, in Wiegmann’s Arch. 
1849, p. 312. es 
Quatrefages. Mémoire sur le Genre Taret (Teredo Lin.), in the Ann. 
d. Sc. Nat. XI. 1849, p. 19. 
Mémoire sur 'embryogénie des Tarets. Ibid. p. 102. 
T. Rupert Jones. Cyclop. Anat. and Physiol. IV. p. 1185, Art. Tuni- 
cata. ; 
G. A. F. Keber. Beitrage zur Anatomie und Physiologie der Weich- 
theire, Kénigsberg, 1851. [Devoted to the nervous, circulatory, and res- 
piratory systems of the fresh-water Bivalvia.] — Ep. 
CHAPTER I. 
CUTANEOUS SYSTEM. 
§ 171. 
The body of the Acephala is enveloped ina special mantle, which, with the 
Tunicata, is composed of a leathery, cartilaginous, or gelatinous substance, 
scarcely at all irritable. But with the Lamellibranchia, and Brachiopoda, 
it is composed of a contractile, fleshy membrane. With the Tunicata, it com- 
1 The maritle is leathery with Cynthia. cartilagi- soft with Salpa, and gelatinous with Clavelina, Di 
uous and hard with Phallusia, cartilaginous and azona, Aplidium, Botryllus, and Pyrosoma. 
