RINGED-WORMS. 215 
a Hemispherical or conical body of about $ millim. terminating in a 
ciliated disc on whose edge the mouth seemed to be placed. At 
the pole of the hemisphere was the anus. This conical body 
increased gradually in length and became divided into rings gra- 
dually more numerous, the last formed ring being that next the 
dise (just as in Escuricnt’s observations on Lothriocephalus the 
new rings were formed in the anterior part of the body). Hach ring 
originally consisted of four pieces: an anterior and a posterior 
piece being larger, almost a semicircle, and a smaller piece on each 
side connecting them. ‘The dise with its vibrating cilia diminished 
gradually and became changed into two fin-like appendages to the 
head, from which the feelers probably proceed!. Sars saw the 
incipient form of Polynoé cirrata as a short, oval, inarticulate body 
with a transverse circle of vibratile cilia round the middle*. It 
may be confidently asserted therefore that there is a metamorphosis ; 
parts are present which afterwards disappear (the vibratile cilia), 
others are deficient which are afterwards developed, and the entire 
form is changed. 
The Reproductive force is, in some animals of this class very 
great, in others small, although worms that have been cut through 
transversely continue to live for a long time, as has been observed 
in the leech, and by O. F. MureLier in Nerets versicolor. TREM- 
BLEY’S experiments on the Fresh-water Polyp induced Bonnet to 
repeat them on Fresh-water Worms (Naides), and he found that 
the pieces he had cut off grew into new worms’. MUELLER also 
succeeded in similar experiments’. It has been thought also that 
they have succeeded in the Earth-worm, but here they have con- 
stantly failed with other experimenters. According, however, to 
the experiments of DuG&s a few rings at the anterior part of the 
body may be reproduced and gradually changed into a head, 
1. Loven, Zoologiska Bidrag; Metamorphos hos en Annelid (Aftryck ur K. 
Vetensk-Akadem. Handlingar, 1840) ; translated into most of the, zoological journals : 
Ann. des Sc. nat. 2e Sér. Xvi. p. 288. 
2 Ericuson’s Archiv. 1845, I. s. 11—1g, Tab. 1. 
3 Observations sur quelques espéces de Vers d’eau douce; Guvres (Edit. 8vo.) pp. 167, 
&e. Especially in Lumbricus variegatus MuEtu. (Lumbriculus variegatus GRUBE) is 
this reproductive power great, in which BONNET saw the amputated head renewed eight 
times in two months. 
4 Von Wiirmern des siissen u. salzigen Wassers, 8. 43, 82, &e. 
> Ann. des Se. nat. XV. 1828, pp. 307, 318. 
