URNATELLA GRACILIS, A FRESH-WATER POLY/OAX. 
13 
In none of the specimens of Urnatella which have come under my observation, 
have I been able to detect the slightest trace of organs of generation or ova. 1 ha\ e 
further been unable to discover distinct elements of a nervous system. At times I 
have thought I could obscurely distinguish the presence of a body in tlie interval 
between the pharynx, stomach and colon, that I suspected to be a ganglion, but 
obtained no definite view of it. 
On the approach of winter, or under unfavorable circumstances, the polyp-bell of 
Urnatella dies and disappears. During the winter the matured segmented stems 
apparently continue alive and unchanged. It has occurred to me that the urn-like 
segments of the stem serve as reproductive bodies, of the nature of tlie statoblasts of 
Plumatella. Ordinarily they do not appear disposed to become isolated or separated 
from one another ; at least I have never obser^'ed them in the latter condition. 
Perhaps, as reproductive bodies, after the polyp-bells perish, they remain in conjunc- 
tion securely anchored through the first of the scries, and are preserved during the 
cold of winter, until under the favorable condition of spring, they put forth buds and 
branches, which, by separation and settlement elsewhere, become the foundation of 
new colonies. In apparent confirmation of this view, I have repeatedly met with 
what appeared to be old stems and fragments of others, which had lo.st their poly{)-bells 
and branches, and from some of the remaining segments had developed new polyi>- 
bells. Such a specimen, collected late in September, 1882, is represented in figure 1). 
Further, I have observed specimens of Urnatella, preserved in an acpiarium, after 
losing their polj^p-bells in the autumn, remain in this condition all winter, and repro- 
duce their polyp-bells the followhig spring. 
Urnatella has the essential constitution of the marine ])olyzoan PedueUlna, and 
clearly forms a genus of the same family. The polyp-bells an? alike in Ibrm and 
constitution. The arrangement of the tentacles and the course and construction of 
the alimentary canal, and the relative position of the oral and anal apertures, are 
the same. 
In Pedicellina, a creeping root-stock or stem is attached to fixed bodies and gives 
off simple pedicels supporting each a polyp-bell. In Urnatella free seginenti'd steins 
■suspended from a fixed point end in a polyp-bell, and give off branches corresimnding 
with the polyp-bell and pedicel of Pedicellina. 
In another genus of the family, recently described by the Rev. T. llincks under 
the name of Barentsia, the polyp-bells are like those of Pedicellina, but are supported 
on pedicels, which arise from an erect and undivided chitinous stem with a bullious 
base. 
The only known remaining genus of the family is Loxosoma, of which then* an* 
a number of species, remarkable generally from their living as parasites on marine 
worms. The species, too, are further remarkable I'rom their occurring as isolat<*d or 
single individuals, corresponding with the polyp-bell and pedicel of the other genera. 
3 JOUR. A. N. S. PHILA., VOL. IX. 
