RINGED-WORMS. 215 



a hemispherical or conical body of about J 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 

 disc (just as in ESCHRICHT'S observations on BoihriocepJialus the 

 new rings were formed in the anterior part of the body). Each 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 disc with its vibrating cilia diminished 

 gradually and became changed into two fin-like appendages to the 

 head, from which the feelers probably proceed 1 . SARS saw the 

 incipient form of Polynoe cir-rata as a short, oval, inarticulate body 

 with a transverse circle of vibratile cilia round the middle 2 . 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 0. F. MUELLER in Nereis 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 3 . MUELLER also 

 succeeded in similar experiments 4 . 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 DUGES a few rings at the anterior part of the 

 body may be reproduced and gradually changed into a head 5 . 



1 S. LOVEN, Zoologiska, Bidrag ; Metamorphos hos en Annelid (Aftryck ur K. 

 Vetensk-ATcadem. Handlingar, 1840) ; translated into most of the. zoological journals : 

 Ann. des Sc. not. IQ Se"r. xvm. p. 288. 



2 EKICHSON'S Archiv. 1845, i. s. n 19, Tab. i. 



3 Observations sur quelques esp&ces de Vers d'eau douce; (Euvres (e*dit. 8vo.) pp. 167, 

 &c. Especially in Lmribricus variegatus MUELL. (Lumbricidus variegatus GEUBE) is 

 this reproductive power great, in which BONNET saw the amputated head renewed eight 

 times in two months. 



4 Von Wurmern des sussen u. salzigcn Wasscrs, s. 43, 82, &c. 



5 Ann. des Sc. nat. xv. 1828, pp. 317, 318. 



