DR. A. FARRE ON THE STRUCTURE OF THE CILIOBRACHIATE POLYPI. 403 
There appears to be but one set of parietal muscles in this instance. The retractors 
of the body resemble those of Bowerbankia, as do also those of the operculum in 
their division into an upper and a lower set, but there appear to be only two instead 
of three of each, as in Bowerbankia (fig - . 4. b.). 
The granules which adhere to the parietes are very distinct in this species, and re- 
main attached to the inner walls of the cell, after the rest of the animal has disap- 
peared (tig. 4. c.), together with the brown bodies which I have conjectured to be 
ovaries or ova. I have not generally observed more than one of these bodies in each 
animal of this species. 
A very remarkable agitation of particles, which was frequently observed in the vis- 
ceral cavity, and very closely resembled the irregular vibration of cilia, was found, 
by the aid of a very high power, to be caused by a multitude of minute cercarice (fig. 5.) 
swimming about with the greatest activity in the fluid with which that cavity is filled. 
When this cavity was laid open by a needle they escaped and swam away by the ser- 
pentine motion of their bodies. They consisted simply of a long slender filament, with 
a rounded extremity, by which they occasionally fixed themselves (fig. 5 • g.). Similar 
parasites were not unfrequently observed in other species. 
The cell is terminated by the usual row of setae (fig. 5 and fig. 6.). Froi'n the 
quantity of earthy material combined with its horny texture, it is rendered so opake 
as to present great difficulty in the examination of the contained parts. This cha- 
racter, which pervades the stem also, renders these parts exceedingly tough and strong; 
and notwithstanding its extreme fineness the stem will bear the exertion of a con- 
siderable degree of force without breaking. When these parts are pressed by the 
dissecting needle they yield a grating sound. 
The arrangement of the cells with regard to the stem is intermediate in regularity 
between that of the two former species. They are generally gathered in clusters which 
surround the stem (fig. 3. a.) ; the cluster nearest to the growing extremity having its 
ceils gradually diminishing in size, and more obviously springing from opposite sides 
of the base of support, the long spiny end of which often projects in a remarkable 
manner beyond the extremity of the branch upon which it creeps. The stem is often 
seen divided into joints at irregular distances,- and the cells are sometimes set on short 
branches springing from them (fig. 3. b.). 
PLATE XXIV. 
Lagenella repens , Mihi. 
Fig. 1. and 2. Parasitic, with a creeping stem, on Sertularia and on Halodactylus 
diaplianus. Not very common. 
This species has twelve ciliated arms (fig. 3. a), not spiny. The alimeutary canal 
is short and stout, and whilst the animal is expanded remains high up in the body. 
During retraction the stomach is never brought down to the bottom of the cell, but 
3 G 
MDCCCXXXVII. 
