Dkckmukk 21, 1S83.] 



SCIENCE. 



(89 



Example 2. Find the reeipiocal of oSOCCi 

 The wliole work is here given : — 



3 3 3 6 6|7 

 233567 



1634 9(ii!i 

 2 1 2 1 3 ~ 



2 2 6 5 5 i>|9 

 2102103 

 23286G|2 

 467134 



700000 



Answer, .O00U0-".)y7. 



Example .'>. Find the reciprocal of 41. 



37|» 



Answer, .02439. 



3 313 



lj_l'- 

 144 

 148' 



1612 

 9» 



C. S. Pkikce. 



URNATELLA GRACILIS, A FRESH- 

 WATER POLY ZO AN. 



A PAPER on this polyzoan, by Professor Joseph 

 Leidy, has been recently publislied, with illustrations, 

 \n t\\6 Journal of Vie Academy of natural sciences of 

 Philadelphia. Urnatella was originally dis- 

 covered in 18.51, and briefly noticed in the 

 Troceedings of the academy the same year, 

 and also subsequently in 1854, 1858, and 

 1870. It was found in the Schuylkill River 

 at Philadelphia, but has not been seen else- 

 where, except a dried but characteristic 

 specimen on the shell of a Unio from Scioto 

 River, Ohio. 



Urnatella is an interesting and beautiful 

 form, living in association with Plumatella 

 and Paludicella, and having similar habits, 

 but is very different from them or any other 

 known fresh-water polyzoan, and is most 

 nearly related with the marine genus Pedi- 

 cellina. It is found attached to the under 

 side of stones beneath which the water can 

 flow. As commonly observed, it consists 

 of a pair of stems divergent in straight lines, 

 or rather gentle curves, from a common disk 

 of attachment. The stems slightly taper, 

 and are beaded in appearance, due to di- 

 vision into segments alternately expanded 

 and contracted. The segments commonly 

 range from two to a dozen, ))roportioned 

 to the length of the stem, which, when 

 longest, is about the eighth of an inch or a little more. 

 The stems terminate in a Ijell-shaped polyp, with an 

 expanded oval or nearly circular mouth slanting to 

 one side, and furnished with about sixteen ciliated 



tentacles. The stems also usually give off a pair of 

 lateral branches from the second segment succeed- 

 ing the polyp, and frequently likewise from the first 

 segment. The branches consist of a single segment 

 or pedicle supporting a polyp, and usually also give 

 off similar secondary braiiche.s. The first and second 

 segments are cylindroid, highly flexible, and mostly 

 striated and colorless, and appear mainly muscular in 

 structure. The succeeding segments are urn-shaped; 

 the body of the urn being commonly i)alo brown, 

 ringed witli lines, and marked with dots of darker 

 brown. The neck and pedicle of the urns are black. 

 The different colors give the stem a beaded and alter- 

 nately brown and black appearance. Through the 

 lighter colored body of the urns a central cord can 

 be seen, extending through the length of the stem. 

 The urn-shaped segments exhibit lateral pairs of cup- 

 like processes, which correspond in position with the 

 branches from the terminal pair of segments of 

 the stem, and apparently indicate branches which 

 have separated from the parent stem to establish 

 themselves elsewhere as new polyp-stocks. 



A series of specimens of 'Urnatella — from such as 

 consist only of a simple cylindrical, flexible pedicle, 

 supporting a polyp, to those with long stems, consist- 

 ing of a dozen segments — indicates the urn-sliaped 

 segments to be formed successively through segmen- 

 tation of the originally single simple pedicle. The 

 segments, therefore, do not correspond with what were 

 polyps; but the terminal polyp is permanent, and the 

 segments originate by division from its neck, very 

 mueli as the segments of the tape-worm arise from its 

 head. After the destruction of the head, the seg- 



3. 1.— rrniilcllii grncilln. The one on llie left willi the pol.vjm expanded; 

 that on the right fn the cundtiion Hssumcd when tho animal is dUturbed. 



mented stem remains persistent; but what becomes 

 of it ultimately has not been determined. Probably 

 the segments may serve tlic purpose of the statoblasts 

 of other fresh-water polyzoa, but the question has not 



