The main results obtained in the present investigation may be summarised as follows:1) In the last premeiotic interphase the nucleus is of the chromonema structure with uniform distribution.2) The first sign of the visible change in nuclear structure in the meiotic prophase is a disturbance in uniformity of the structure taking place gradually in the nucleus. The coiled aspect of the chromonemata becomes then more and more conspicuous, and the whole chromosomes can be traced for some considerable length.3) The disturbance in the uniformity of the nuclear structure is due to the contraction or condensation of the chromosomes which are previously in the diffuse state. At the maximum condensation, the chromosomal bodies are distinguishable clearly from one another, the interchromosomal clear spaces being distinct, though a certain complication prevents us from the exact counting of their number. This stage correspond with the stage known as the “spiral stage” in somatic mitosis.4) The condensed chromosomes are unravelled and the fine leptotene threads come out of them. The unravelling takes place without showing any marked change in the thickness of the chromonema threads in striking contrast to the case of the somatic mitosis where the threads become remarkably thicker than before unravelling.5) The “Ansammlung der Chromatinkörner” seen in older literature seems to correspond with the chromosome condensation which we understand as the first stage observable distinctly in meiosis.The writer wishes to acknowledge his sincere gratitude to Prof. Y. KUWADA for his kind guidance and encouragement throughout the course of the present investigation.