DR. A. FARRE ON THE STRUCTURE OF THE CILIOERACHIATE POLYPI. 409 
The peculiar fleshy character which caused the name gelatinosum to be applied 
to this species arises from the mode in which the cells are united together. Their 
arrangement is best seen by making a thin transverse slice of the main substance and 
examining it with a low power (Plate XXV. fig. 3.). The cells are then found to be 
arranged parallel with one another and having their sides united together so as to 
form a compact ring, of which the bases constitute the inner and the apices the outer 
circumference. The centre of the cylinder, of which this is a section, is occupied by 
a light cellular tissue and a clear fluid, probably water. In such a section similar 
brown bodies to those already described are seen in great numbers, and not confined 
to the cells, but dispersed through the whole substance. The arrangement of the 
cells being thus shown, a more accurate view of their structure is obtained by exami- 
ning a thin section made parallel with the surface (fig. 4.). In this view their ends 
only are seen having an hexagonal form, from their pressure upon each other, but in 
each compartment the animal may be discerned with all its parts. Sometimes, how- 
ever, the cells, instead of being arranged parallel to one another, lie so obliquely, that 
their sides instead of their apices form the outer surface ; an arrangement which 
bears a close resemblance to that of the cells of Flustra (fig. 5.). But in order to 
witness the different stages of protrusion and retraction a portion of the mass must 
be viewed edgewise (Plate XXV. fig. 2. and Plate XXVI. fig. 7-)* I n which position, 
although the lower part of the cell and animal is generally concealed from view, all 
the most interesting parts may be observed as they rise in succession above the sur- 
face. The stages of protrusion and retraction occur in the same order and with 
nearly the same phenomena as in Bowerbankia. (See the series from fig. 11 to 16. 
Plate XXVI.) The arms, however, instead of rising straight are often seen bent upon 
themselves, a provision that appears to be necessary, on account of the great length 
of some of them, in order that they may be completely inclosed in the cell. 
The upper portion of the cell, from its superior transparency and flexibility, ap- 
pears to contain little, if any, earthy matter. The setse (fig. 7- « andc?.) are very stout 
and short, broad at their base, and few in number. The body projects to an unusual 
distance beyond the mouth of the cell (fig. 7- «.), and its delicate parietes may be 
seen separate from the whole circumference of the cell, except where they are attached 
to the edge of the operculum at the point whence the setee arise. 
Cercarise were seen in the bodies of these animals which did not differ in any re- 
spect from those of Valkeria, and occupied a similar position. On one occasion these 
were observed drifting rapidly to the upper part of the visceral cavity, and shortly 
after issued from the centre of the tentacula ; but as the animal had in the mean time 
half withdrawn itself, I lost the opportunity of tracing their course. It would appear 
from this that there is some external communication with the cavity of the body. 
The process of reproduction by gemmation (in this case by the growth of young 
animals and cells amongst the mature ones) may be seen in every specimen (Plate 
XXV. fig. 4.). The smaller cells are triangular, and the animal forms a mere spot in its 
