The spermatogonia are formed anew each season from cells which migrate from some point outside the lobule, possibly in some cases even from outside the testis. Evidence points to the presence of definite pro-chromosomes in the early spermatogonia. These elements serve as aggregation centers for the 22 spermatogonial chromosomes. Chromosomes, at different times and in different cells, may exhibit contractions of varying degrees. Extreme contraction simulating a transverse fission is unusual. Such transversely constricted chromosomes are limited to certain spermatogonial divisions and play no part in the maturation divisions. Two large L-shaped chromosomes, relatively constant in size and shape, which may be sex-chromosomes, are often found. Pronounced increase in cell size does not occur in the primary spermatocyte stage but takes place in the early spermatogonia. The primary spermatocytes show slight increase in size over the spermatogonia of the preceding multiplication division. The 11 chromosomes emerge from synizesis as rods or blocks of chromatin of varying length and thickness; during diakinesis they form tetrads of the closed ring type. The secondary spermatocytes may go into a resting stage but usually the telophase of the primary spermatocyte passes immediately into the metaphase of the 2nd maturation division. At the beginning of spermi-ogenesis the chromatin collects along the linin of the nucleus in a rather scattered condition in which roughly 7-11 chromatin masses may be distinguished. The behavior of the chromatin masses is indicative of chromosome formation for the metaphase of another division. These small chromatin bodies go through an apparent fusion in pairs, with a subsequent peripheral condensation of the chromatin, and a contraction of the entire nucleus as the head of the spermatozoon forms.