EEPOET ON THE TUNICATA. 
61 
Ascicliozooids ova are present in two masses, one on eacli side of the body near the 
posterior end, but in the fully developed condition no ova are present, and the irregularly 
stellate genital gland is formed entirely of spermatic vesicles. 
An extraordinarily large number of tailed larvae are present in the colony. They 
appear to be all at the same advanced stage of development. Only one pigmented sense- 
organ is present ; it is placed to the left of the middle line when the body is viewed from 
the dorsal surface. The shape of the body of the larva varies according to the point from 
which it is viewed. When seen from the side (PI. IV. fig. 17) it is equally wide in 
front and behind, while the dorsal or the ventral aspect shows the posterior end much 
narrower than the anterior (PI. IV. fig. 16). The urochord is very distinct, and is 
formed of a single series of large cubical cells (see PI. IV. fig. 18). 
Polycyclus, Lamarck. 
Pohjcydus, Lamarck, M^m. Mas. Hist. Nat. Paris, t. i., 181. 5. 
Botryllus, Savigny, Mem. Anim. s. vert., pp. 47, 202, 1816. In part. 
Puhjcychis, Eisso, Hist. Nat., &c., t. iv., Paris, 1826, p. 280. 
Polycyclus, Lamarck, Hist. Nat. Anim. s. vert., vol. i. p. 57.5, 1837. 
Polycyclus, Delle Chiaje, Descrizione e Notomia, &c., t. iii. p. 19, Najj., 1841 (as a subgenus). 
Botryllus, IMilne-Echvards, Observations, &c., 1842. In part. 
Botryllus, Forbes and Hanley, Britisb Mollusca, vol. i., London, 1853. In part. 
Botryllus, Grube, Die Insel Lussin, &c., p. 64, Breslau, 1864. In part. 
Botryllus, Giard, Eechercbes sur les Synascidies, p. 619, Paris, 1872. In part. 
Polycyclus, Della Valle, Contribuzioni, &c., p. 22, Napoli, 1877 (as a subgenus). 
Polycyclus, von Drascbe, Die Synascidien der Bucbt von Eovigno, p. 13, Wien, 1883 (as a 
subgenus). 
Colotiy thick, fleshy, and often lobed. 
Systems circular in outline. 
Ascicliozooids ovate, with the apertures rather distant from one another. 
Test gelatinous, but solid and much thickened, vessels present. 
Branchicd Sac large and well developed. 
Tentacles from two to sixteen in number. 
Alimentary Caned placed alongside the posterior end of the branchial sac. 
Re^roduetive Organs placed on both sides of the body near the posterior end. 
This genus, although founded as far back as 1815, has been by no means generally 
accepted by writers on the Tunicata, most of whom have included Lamarck’s species in 
the genus Botryllus. 
Della Valle in 1877 characterised Polycyclus afresh, and regarded it as being of equal 
rank with Botrylloides, both being subgenera. On the other hand, von Drasche considers 
Botrylloides as a distinct genus, and Polycyclus as merely a subgenus of Botryllus. I 
prefer, as explained before (p. 36), to regard these groups of species as being all of 
