146 ZOOLOGY. 
Ciass IV.—POLYZOA. 
Animals usually forming moss-like or coral-like calcareous or chitinous 
masses called corms, each cell containing a worm-like animal, with the di- 
gestive tract flewed, the anus situated near the mouth. The body usually 
drawn in and out of the cell by the action of retractor and adductor muscles. 
The mouth surrounded by a crown of long tentacles. No heart or vascular 
system. Nervous system consisting of a single or double ganglion situated 
between the mouth and vent, with nerves proceeding from tt. Hermaphro- 
ditic ; multiplying by budding or eggs. The embryo passing through a 
morula, gastrula and trochosphere stage, the corm being formed by the 
budding of numerous cells from a primitive one, 
Order 1. Entoprocta.—Vent within the lophophore. (Loxosoma.) 
Order 2. Ectoprocta.—Vent without the lophophore. (Lepralia, Es- 
chara, Idmonea, Myriozoum.) 
Laboratory Work.—The Polyzoa are too small to dissect, and 
must be studied while alive as transparent objects, and may be kept 
in aquaria. The corms in part or whole can be mounted for the mi- 
croscope as opaque objects. 
Ciass V.—BracHiopopa (Lamp Shells). 
General Characters of Brachiopods.—This group is named 
Brachiopoda from the feet-like arms, fringed with tentacles, 
coiled up within the shell, and which correspond to the 
lophophore of the Polyzoa and the crown of tentacles of the 
Sabella-like worms. From the fact that the animal secretes 
a true, bivalved, solid shell, though it is usually inequivalve, 
i.e., the valves of different sizes, the Brachiopoda were gener- 
ally, and still are by some authors, considered to be mol- 
lusks, though aberrant in type. They may be regarded as a 
synthetic type of worms, with some superficial molluscan 
features. The shell of our common northern species, Tere- 
bratulina septentrionalis, which lives attached to rocks in 
from ten to fifty or more fathoms north of Cape Cod, is in 
shape somewhat like an ancient Roman lamp, the upper and 
larger valve being perforated at the base for the passage 
through it of a peduncle by which the animal is attached 
to rocks. The shell is secreted by the skin (ectoderm), and is 
