BRITISH MARINE POLYZOA. 79 
names, as the ‘“ Birds’ Head Coralline,” are names which could 
only have been derived from accurate microscopical observations, 
as the peculiar features from which the names are taken are 
invisible to the naked eye. Ellis dedicated his book to the Princess 
Dowager of Wales, and informed us that in autumn, 1751, he re- 
ceived a curious collection of sea-plants and corallines from 
Anglesea, &c., and laid them out under fresh water in a manner 
fitted to show their ramifications, &c. These, when properly dried, 
he disposed on boards covered with clean white paper in such a 
manner as to form a kind of landscape, showing hills, dales and 
rocks, which made a proper groundwork for the little trees which 
the expanded sea-plants and corallines not inaptly represented. The 
Rev. Dr. S. Hales, who visited him, was so pleased with these that 
he asked him to make some more for the Princess Dowager of 
Wales, so that the young princesses might amuse themselves in a 
similar manner. In order to carry out this desire, he began to 
classify his specimens, and (happy thought) to examine them with 
his microscope, which he figured in his work, and which certainly 
makes us feel that we ought to make something out of our perfect 
instruments after seeing his success with his primitive lens. His 
attention was directed to their nature, and he went to the Island of 
Sheppey, taking with him Mr. Brooking, a celebrated painter of 
sea pieces, to draw for him. On watching the organisms alive, he 
came to the conclusion that the apparent plants were really ‘ rami- 
fied animals in their proper skins or cases, not locomotive, but 
fixed to shells of oysters, mussels, &c., and to various fuci.” In his 
book he describes the structure, as it appeared to him, of the 
zoophytes found by him, and classifies them so far as his observa- 
tions would permit. From this pictorial origin we may trace a 
careful succession of students of zoophytes, particularly Johnston, 
Landsborough, Aldis, Allman, and Hincks, the last-named of whom 
has completely studied andclassified both the Polyzoa and Hydrozoa, 
and his works on both subjects contain perfectly executed plates of 
nearly all the known British species. 
The first question which we have to inquire is, What is a Polyzoon? 
It is an animal allied to the Mollusca, consisting of two parts, a 
polypide and a zocecium, z.¢., an animal and its cell; but we must 
bear in mind that the cell is a part of the animal. The polypide 
consists of a tube bent upon itself so that its two orifices approxi- 
mate, the oral or mouth orifice being provided with a ring of 
tentacles, which are ciliated. This tube contains the cesophagus, 
stomach, and intestine, and on the side nearest the oral orifice is a 
nervous ganglion. This tube is enclosed in a sac containing fluid, 
which is called the zocecium. This sac has two openings through 
which the tentacles protrude and the anal orifice leads—the interior 
lining of the zocecium is extended so as to form a sheath to the . 
