SPERMATOZO'A is the term given to the true fertilizing agents occurring in the male genetatt organs. They appear to be formed from the epithelial Dining of the tortuous semina lies, of which the organ known as the testis is essentially composed. At the period of puberty in man, and at certain periods annually in other animals, the seminal tubes are seen to be filled with cells, from which the spermatozoa are developed. With out describing the various changes that ensue, we may observe, that the spermatozoa are finally set free by the bursting of the cell-walls, and arrange themselves in po•cels sym metrically placed, with the so-called bends in one direction, and the tails in the opposiin direction. III the human subject, the spermatozoa may be described as clear, hyaloid bodies, each of which consists of a dilated portion, the head or body, from which a long tail, or filament, issues. The head is flattened from side to side, and of a conical form,
the pointed extremity being anterior. The length of the spermatozoa is about of of an The spermatozoa of different animals vary extremely in size and form; and for a detailed account of these bodies, in different classes of animals, we must refer to the article "semen," in the Cyclopmdia of Anatomy and Physiology. It was formerly sup posed that spermatozoa were independent organisms (like the infusoria for example), but it is now known that they must be regarded as epithelial cells (or perhaps nuclei), modi fied in structure, and endowed with special properties. That the integrity of the sper matozoa is essential for the process of impregnation, is a fact that cannot he called in question; but of the nature of the force which they communicate to the ova, we know nothing.