Mounting Work on Mandrels To machine a workpiece of an odd shape, such as a wheelpulley, a tapered mandrel is used to hold and turn the work.The mandrel must be mounted between centers and a driveplate and lathe dog must be used. The centers must be alignedand the mandrel must be free of burrs.
Rotifers: the wheel animalcules. Rotifers are microscopic aquatic animals of the phylum Rotifera. Rotifers can be found in many freshwater environments and in moist soil, where they inhabit the thin films of water that are formed around soil particles.ther animals with a pseudocoel, such as rotifers and acanthocephalans, appear to be more closely related to Lophotrochozoa, a large alliance of protostomes that includes molluscs, annelids, brachiopods, etc. Phylum Rotifera is divided into three classes: Monogononta, Bdelloidea, and Seisonidea.
Phylum Chordata. The phylum Chordata contains all animals that possess, at some point during their lives, a hollow nerve cord and a notochord, a flexible rod between the nerve cord and the digestive track. The phylum Chordata is an extremely diverse phylum, and the one most recognizable to us. The phylum contains about 43,700 species, most of them concentrated in the subphylum Vertebrata, making it the third-largest phylum in the animal kingdom. The phylum Chordata is divided into three subphylums: Urochordata (tunicates), Cephalachordata (lancelets), and Vertebrata (vertebrates). The first two phyla are very small containing only about 2,000 species total.