fod 
BRYOZOA, WITH DESCRIPTIONS OF NEW SPECIES. 317 
Nervous System.—Some years ago Professor Allman discovered 
a ganglion in these animals, and has more recently ascertained 
the existence of nerves. I have also detected a large ganglion, 
Pl. III. fig. 1 &, in Plumatella and Fredericella. It is situated 
just below the entrance to the csophagus, on the external sur- 
face, close to the base of the tentacles and just above the anal 
orifice. It is therefore placed between the oral arms in Plwma- 
tella, and in Fredericella at the corresponding point. In the 
latter I have observed two or three nerves passing from the 
ganglion upwards in the direction of the tentacles, and one 
apparently going to embrace the oesophagus ; another that comes 
from the lower extremity of the ganglion may also be seen pas- 
sing downwards close to the esophagus. This is all I have been 
able to make out respecting the nervous system, though 
undoubtedly more is to be learnt. © 
Muscular System.—There are three distinct set of muscles in 
Plumatella and Fredericella; one for the retraction of the 
polype, another to assist in the act of protrusion, and the third 
probably accessory in closing the orifice. The first and most 
conspicuous set of muscles, the polype retractors, Pl. III. figs. 2 g, 
g &4f, and Pl. IV. figs. 4 g & 5 7, 2, is divided into two equal 
bundles, one passing on each side of the polype. These bundles 
are composed of numerous, stout, isolated fibres, having their 
origin in the walls of the cell a considerable way below the 
retracted polype ; and passing upwards have their superior ex- 
tremities inserted at the tentacular disc or base of the oral arms 
and at the upper portion of the esophagus. There are also two 
sunilar bundles of muscular fibres in Alcyonella, but in this 
genus they have their origin at, or close to, the bottom of the cell. 
When the animal of Plumatella is exserted, two or three of the 
stoutest, Pl. III. fig. 4 g, of these fibres are seen to be attached on 
each side further forward than the rest at the base of the oral 
arms. Also in /redericella similar fibres are inserted at the 
corresponding parts of the tentacular disc. These stout fibres 
have their origin a little lower down the cell than the rest. 
_The function of these two bundles of muscular fibres cannot 
for a moment be mistaken: they are for the purpose of drawing 
