Page:A Text-book of Animal Physiology.djvu/51

Rh possibly the clear fluid with which they are filled may be a special secretion with solvent action on food.



Situated somewhat centrally is a horseshoe-shaped body, with well-defined edges, which stains more readily than the rest of the cell, indicating a different chemical composition; and, from the prominent part it takes in the reproductive and other functions of the creature, it may be considered the nucleus (endoplast). Multiplication of the species is either by gemmation or by fission. In the first case the nucleus divides and the fragments are transformed into locomotive germs; in the latter the entire animal, including the nucleus, divides longitudinally, each half becoming a similar complete, independent organism. Still