76 
CLASSIFICATIONS OF ZOOPHYTES. 
the mouth encircled with roughish filiform tentacula ; stomach with- 
out proper parietes ; intestine 0 ; anus 0 ; reproductive gemmules 
pullulating from the body and naked, or contained in external vesi- 
cles. Polypidoms horny, fistular, more or less phytoidal, fixed, ex- 
ternal. Marine, excepting Hydra , which is lacustrine. 
Order II. Asteroid a. Polypes compound, the mouth encircled 
with 8 fringed tentacula; stomach membranous, with dependant 
vasculiform appendages ; intestine 0 ; anus 0 ; reproductive gem- 
mules produced interiorly. Polype-mass variable in form, free or 
permanently attached, carnose, generally strengthened with a horny 
or calcareous axis enveloped with the gelatinous or creto-gelatinous 
crust in which the polype-cells are immersed, and which open on the 
surface in a starred fashion with eight rays. Marine. 
Order III. Helianthoida. Polypes single, free or permanently 
attached, fleshy, naked or encrusted with a calcareous Polypidom, 
the upper surface of which is crossed with radiating lamellae ; mouth 
encircled with tubulous tentacula ; stomach membranous, plaited ; 
intestine 0 ; anus 0 ; oviparous, the ovaries internal. Marine. 
Sub-Class II. MOLLUSCAN ZOOPHYTES. 
Pody non-contractile, and non- symmetrical ; mouth and anus 
separate ; gemmiparous and oviparous. 
Order IV. Ascidioida. Polypes aggregate, the mouth encircled 
with filiform ciliated retractile tentacula ; a distinct stomach, with 
a curved intestine terminating in an anus near the mouth ; ova in- 
ternal. Polypidoms very variable, — either horny, fistular and con- 
fervoid, or calcareous, membranous, or fibro- gelatinous, formed of 
cells connected and arranged in a determinate and usually quin- 
cuncial manner. Marine and lacustrine. 
Additional Note. 
The only extensive series of experiments we have on the composition of 
Polypidoms are those of Mr Hatchett, published in the Philosophical Transac- 
tions for 1800 , and the subsequent progress of zoological and chemical science 
requires a new investigation of the subject. The general results of Mr Hatch- 
ett’s experiments are, “ that the Madrepores and Millepores are formed of a ge- 
latinous or membranaceous substance, hardened by carbonate of lime, the differ- 
ence consisting only in the mode in which these materials are combined : that 
in the Tubipora, Flustra and Corallina, some phosphate of lime is mixed with 
the carbonate of lime : that in the Isis the basis is a regularly organized mem- 
branaceous, cartilaginous and horny substance, hardened by carbonate of lime, 
one species only (the Isis ochracea) yielding also a small proportion of phos- 
phate of lime. That the hardening substance of the Gorgonia nobilis is like- 
wise the carbonate of lime, with a small portion of phosphate ; but that the 
matter forming the membranaceous basis consists of two parts, the interior being 
