Horváth Géza (szerk.): A Magyar Természettudományi Múzeum évkönyve 8. (Budapest 1910)
Soós, L.: A Helix arbustorum hím csirasejtjének fejlődése
324 LH L. SOÓS in ovogenesis). P OPOFF emphasizes that the resemblance in ovogenesis of Mammals and Paludina is so great that it extends even to details. As these observations show, an intercalated resting period in the development of the ovocytes is not rarely to be found during which the earlier formed chromosomes become dissolved, and even disappear, as CARNOY and L EBRUN observed in the ovocytes of Amphibia. The matter is otherwise, as a rule, in spermatocytes. In the liteiature known by the present author only one contribution is to be found, according to which the chromosomes of the spermatocytes in a certain period disappear and the nucleus becomes a «resting» one Notodromas monacha, SCHLEIP (107)]. POPOFF (94) put the question what circumstances cause the resemblance in ovogenesis of Mammals and Paludina ? This question also interests us, because not only is the ovogenesis of Mammals very similar to that of Paludina, but also the behavior of the spermatocytes of //. arbustorum agrees in some respects with that of the ovocytes of the animals mentioned. POPOFF refers to the similarity in the development of the eggs which is a result of the viviparism. The ova of the viviparous animals ripen at large intervals, for instance Paludina produces one egg a week. The ovocytes in the second part of the growth period form a constant stock from which from time to time one ripens, therefore their resting stage is easily to be understood. This explanation is not applicable to II. arbustorum, since the spermatocytes do not stay for a longer time within the genital gland like the ova of Paludina, or of the Mammals. I claim as explanation the fact referred to formerly by W OLTERECK (128\ and recently by R. HERTWIG (49), according to which the cell prepares in the first part of the growth period for division. The preparing for division is shown by the phenomena of the transformations of the chromatin, in the forming of definite chromosomes and their splitting. The division, however, does not take place, i. e. we have to do with a division suppressed by some cause, but it is followed, according to the rules of the division, by a « resting stage». I believe that this suppressed division may be explained upon the base of the theory of the nucleo-plasmic ratio of R. HERTWIG, upon which also POPOFF (94) explained the suppressed divisions in ovogenesis of Paludina. The spermatogonia may be compared to the Protozoa cells the depressions of which become balanced by frequent divisions, but the energy of the cells after the last spermatogonial division becomes exhausted so much in the struggling against the preceding depressions, i. e. the depression becomes so strong that a single division is no more sufficient to balance it, and division cannot be completed.
