11 



muscles. These jaws keep up a continual opening and shutting 

 movement. The head is also articulated to a sort of neck, and 

 sways to and fro, presenting the front of the jaws in different 

 directions. Out of forty-five British species avicularia may be found 

 in thirty-one, but not all of the same design ; they vary from the 

 most simple rudimentary forms to the complex " bird's-head." 



The vibraculum is a kind of movable bristle working in a socket 

 by powerful muscles. At intervals it sweeps round and clears away 

 all refuse matter which would interfere with the health of the 

 colony. 



Vibracula are much rarer than avicularia, only being found on 

 four species ; on two species both appendages are present. 



The two organs have quite different functions. The " bird's- 

 heads " are evidently for the capture of food for the colony, for the 

 jaws are seen to snap up any passing creature and to hold it until 

 dead and decomposing. Then the surrounding ciliary action of 

 the polypides draws the particles to them, and thus the whole 

 colony is nourished. 



The Polyzoa have two methods of reproduction— by ova and by 

 gemmation. 



The ova are fertilised by spermatozoa discharged into the sur- 

 rounding water. From the ova are developed free swimming 

 (infusoria-like) beings of various shapes ; these after a time settle 

 down and begin a new colony. 



The other method of reproduction is by gemmation. The colony 

 extends from its edges by outgrowths, as it were, which form cells 

 and develop young polyps. 



In one eNample- — the Loxosoma — the young detach themselves, 

 and are developed into solitary animals. These belong to the Ento- 

 procta group. 



The variety of designs in the grouping of cells is innumerable. 

 Sometimes the polyzoon will attach itself to a piece of sea-weed, 

 spread along the frond, and eventually cover it with a calcareous 

 mat. It is popularly known as Sea Mat. There are various species 

 that develop in that manner, each species having a differently 

 designed cell. Some prefer a stone or piece of rock to build upon, 

 others choose something which has movement — such as the leg of a 

 crab or lobster, or a whelk-shell. Many beautiful forms are found 

 attached to shells. 



A few species are found in fresh water, sometimes attached to the 

 roots of submerged trees, or on the under-side of aquatic vegeta- 

 tion — frequently on the leaves of the water-lily. 



One species has the faculty of shifting its quarters and roaming 

 from plant to plant. 



I am afraid I have treated this subject in a very cursory way. It 

 is so large that it is difficult to know what to say to do the matter 

 justice. Any one species, with its life history, anatomy, and 

 physiology, is sufficient for an evening's discourse, and if I have 



