From its body, which, when at rest, is nearly spherical, it is almost constantly casting forth certain “finger-like processes” which are as quickly withdrawn, only to reappear on some other portion of its surface. The small particles of albuminous matter with which it comes in contact adhere to it, or are drawn into its semi-fluid body by displacement of the several albuminous particles of which it is composed, and are there digested, being “absorbed by simple diffusion.” Its only activity consists in supplying itself with nourishment, and even during this process it is said to display a negative or passive quality rather than real action. The particles absorbed that are not assimilated, are expelled through the surface of the body in the same manner as they are taken into it. At first, we are told, our animal is only a simple cell, in fact that it is not a perfect cell, for as yet the cell-kernel or nucleus has not been separated from the cell-substance or protoplasm. When its limit of size has been reached it multiplies by self-division, or by simply breaking into parts, each part performing the same functions of nutrition and propagation as its predecessor. Later, however, when a parent cell bursts, the newly developed cells no longer separate from it, but, by cohering to it and to each other, form a cluster of nucleated cells, while around this aggregation of units is formed a wall. Still its food is absorbed. Subsequently, however, a mouth and prehensile organs for seizing its food are developed, and the divisions between the cells are converted into channels or pipes through which nourishment is conveyed to every part of the body. In process of time, limbs for locomotion appear, together with bones for levers, and muscles for moving them. Finally, a brain and a heart are evolved, and although at first the heart appears as only a simple pulsating vessel, later this animal finds itself the possessor of a perfect system of digestion, circulation, and excretion, by which food, after having been changed into blood and aërated or purified by processes carried on in the system, is pumped to every part of the body. With the formation of different chemical combinations, and the development, through increasing specialization of the various kinds of tissues, and finally of the various organs, that intimate relationship observed between the parts in homogeneous and less differentiated structures no longer exists; hence, in response to the demand for communication between the various organs, numberless threads or fibres begin to stretch themselves through the muscles, and collecting in knots or centres in the brain and spine, establish instantaneous communication between the different parts, and convey sensation and feeling throughout the entire organism.