310 Miscellaneous. 



ehmgata, PlumateUa vesicuhiri^, and the worm ManayunTcla sjoe- 

 ciosa, &c. 



Uulike the marine genera of Pedicellinida?, the polyp-stocks of 

 Urnatella are erect or semiercct, and not prostrate or creeping at- 

 tached along the surface of bodies. Urnatella starts by a thin 

 membranous disk or expansion tightly adherent to the point of sup- 

 port. Usually two stems or stocks (occasionally three or only one) 

 start from the same disk, and diverge from each other in a gentle 

 curve. The stems may be seen from a simple pedicle without divi- 

 sion to a series of eleven divisions or segments, exclusive of the 

 pol}"p-head. A colony of Urnatella recalls to mind a miniature 

 patch of plants in a flower-garden. The smallest polyps are trans- 

 lucent whitish or nearly colourless ; the largest are less than two 

 lines long, and alternately white and blackish or brownish. When 

 disturbed, the polyps retract their arms, hang their heads, and bend 

 downward, so that the heads touch the basis of support, or the stems 

 even become somewhat involute. Voluntarily the polyps are often 

 observed abruptly to move from one side to the other in the most 

 singular manner, as if wearied of remaining too long in the same 

 position. In these movements the stems bend the entire length, 

 but there is no contraction or shortening. In attempting to detach 

 a polyp, the heads suddenly bend downward in such a manner as if 

 the violence elicited a feeling of pain in the animal. 



The terminal two or three segments of the parent stems usually 

 give off a branch on each side ; and this branch sometimes gives off 

 a second. The branches always consist of a pedicel or single joint 

 supporting a polyp-head. 



In a polyp-stock of more than two di\dsions, independent of the 

 polyp-head, the additional segments are urn-shaped. The penulti- 

 mate segment is barrel-shaped ; the last one cylindrical or clavate. 



The polyp-heads are provided with from a dozen to sixteen ciliated 

 arms. The internal structure of the polyps, including that of the 

 stems, bears a resemblance to that of Pedicellina, and will be more 

 particularly described in a memoir preparing on the animal. 



The youngest independent polyp-stems of Urnatella consist of a 

 simple cylindrical pedicel starting from the disk of attachment to 

 the rock, and supporting a single polyp-head. The pedicel elongates 

 and divides into two segments. The ultimate segment grows in 

 length, and again divides ; and in this manner all the segments are 

 produced. After the production of three segments, the antepenulti- 

 mate segment assumes the urn-form. Budding commences from the 

 second and third segments after their production, and from the suc- 

 ceeding segments, but not usually from the first segment. The buds 

 originate from opposite sides of the base of the segments, and form 

 branches of a single segment with a polyp-head. The pedicel of 

 these branches also frequently gives off a bud, which forms a secon- 

 dary branch of the same kind as the primary ones. 



In the longer Urnatella-stocks branches are usually observed only 

 from the one, two, or three terminal segments. In the posterior 

 urn-shaped segments, in the position in which branches emanate in 

 the terminal segments, cup-shaped processes are observed. These 



