84 THE MICROSCOPICAL NEWS. 
much questioned. Some have regarded them as food providers, 
and they have been observed to hold small worms, but as they 
cannot transfer the worms to the mouth they are useless for this 
purpose, and are now regarded as defensive in their functions— 
serving to drive away by their appearance or movements any 
enemies of the colony. 
The Vibrvaculum is a chamber in which muscles are lodged, and 
contains a moveable bristle. This is of rare occurrence, and is 
generally placed in such a manner as to sway backwards and for- 
wards across the opening of the zocecium, and may serve the 
purpose of keeping clear from hindrances and accumulations of 
matter the entrance of the cells. 
The reproduction of the polyzoa is of two kinds—sexual and 
asexual. In the latter case gemmation is the modus operandi. 
The reproductive elements have already been explained as having 
their origin in the endosarc, and their position in the perigastric 
cavity. In some species there is an intertentacular organ or open- 
ing between the tentacles to allow of the escape of the spermatozoa. 
The ovary contains sometimes thirty ova—sometimes only two. 
After fertilization the usual course of segmentation takes place— 
resulting in a free ciliated larva. In many species of the Chez- 
lostomata ovicells are developed in the breeding season, at the 
upper extremity of the cell. This usually occurs by gemmation 
from the wall of the zocecium. ‘The interim is in direct com- 
munication with the perigastric cavity. These ovicells serve, 
according to Professor Huxley, for marsupial chambers, where, 
after fertilization, the ova develop into the larva, and from whence 
the larvee escape into the outside world. The larvee are varied in 
form—some singularly beautiful in colour, and some are even 
furnished with a bivalve shell. They are restless in their habits, 
and are richly ciliated. After a while the restlessness ceases. 
The larva settles down into an apparently homogeneous mass, 
which is the first zocecium and polypide, and assumes the perfect 
form after a process of histolysis. 
The Polyzoa are also reproduced by gemmation, which is con- 
tinuous—the different cells (except in Loxosoma) not falling off, 
but continuing as part of the colony. The buds are produced 
from the endosarc, and speedily assume the perfect form. 
Having now described the structure of the Polyzoa it remains 
to enquire into their place in nature. Linnzeus classed them as 
worms in common with Hydra, tape worms, Volvox, and others. 
It will be needless to follow the many classifications since his time, 
but it may be pointed out that at present some writers consider 
them as worms, others as Rotifers, others as Coelenterata, and 
others, including Milne-Edwards, Agassy, Allman, Huxley. 
Ray-Lankester, Hincks, and others, assign them to the Mollusca, 
