To thoroughly appreciate the beauty of these organisms they 

 must be seen alive. The chitinous coverings which we pick up on 

 the sea-shore are beautiful, but will not bear comparison with the 

 beauty of the living animals, which, when placed in sea-water, project 

 themselves and assume the appearance of blossoms on some graceful 

 plant, and frequently of gorgeous colours. 



Not only is their form a delight to us, but their habits exert a 

 certain amount of fascination and respect from us ; as each animal 

 works for the commonwealth, as well as itself, there can be no 

 selfishness amongst them, as the food each one captures goes to 

 nourish the whole colony. 



The classification of the Hydroid Zoophytes is very complicated. 



I will not trouble you with the names of the different species, but 

 merely say that they are placed in the sub-kingdom Ccelenterata, 

 class Hydrozoa ; this, again, is divided into various orders and sub- 

 orders, containing numerous families. To describe the peculiarities 

 of each family would alone occupy the whole evening, and would 

 not, I think, be particularly interesting to my hearers. 



Polyzoa. 



Having given you a short and somewhat meagre description of 

 the Hydroid Zoophytes, I propose to say a few words upon the 

 Polyzoa, which by the older writers were included in the term 

 " Zoophyte," but being of far more complex structure are now 

 classified in the sub-kingdom Molluscoidea, branch Acephala, and 

 class Polyzoa, which is again divided into various sub-classes, orders, 

 and families, too numerous to take up your time with this evening. 



There is a very great difference in the appearance of some of the 

 families, and yet a gradual development may be traced from the 

 simpler to the more complex forms. 



The difference is not so marked in the polyp itself, but in the 

 zoarium — the collection of cells or homes. 



When a larva attaches itself, it becomes changed into a single 

 cell containing certain elements in a rudimentary condition ; these 

 after a time become developed into a polypide. By continuous 

 budding the composite zoarium is built up. 



You will see by the diagram that the polypide consists of a tube 

 varying in diameter, with two openings — one the mouth situated in 

 the centre of the ring of tentacles, the other the anus, both opening 

 on the outside of the membranous sac, which is filled with fluid. 

 This sac at its extremity is soft and flexible, and by means of 

 suitable muscles the polypide can retreat or draw its tentacles in, 

 the sac also turning in upon itself, forming a sheath as it were 

 around the tentacles, when the animal retires into its cell. 



The cell, or zocecium, varies much in shape (according to the 

 species) ; it consists of two walls — the outer (ectocyst) and the inner 

 (endocyst). 



