Horváth Géza (szerk.): A Magyar Természettudományi Múzeum évkönyve 8. (Budapest 1910)
Soós, L.: A Helix arbustorum hím csirasejtjének fejlődése
SPJ^ MIOGENESIS OF HELIX ARBUSTORUM. 325 This depression becomes balanced by a casting of chromatin into the cytoplasm. The chromatin thus thrown forms the chromidia. This hypothesis may be supported by the fact that the chromidia first appear close to the nuclear membrane, and lie at the open ends of the loops. The connection is so regular that we must assume a nuclear origin of the chromidia, as it has been shown by E. HERTWIG in Protozoa. It was observed by several authors that chromatin gets from the nucleus into the cytoplasm, for instance : G OLDSCHMIDT (32) observed the process in Ascaris , MATHEWS in the pancreas cells of Amphibia, HENSCHEN (47) in ova of Helix pomatia, STEVENS (115) in ovocytes of Sagitta, A. and K. E. S CHREINER (111) in spermatocytes of Myxine glutinosa, etc. Chromidia can be found in the cytoplasm also earlier, by which is shown that the suppression of the depression by the casting out of a part of the chromatin begins earlier, but the real formation of the chromidia only takes place after the suppressed division. This explanation has a difficulty, viz., it is difficult to understand the great capacity of the pachytene cell for absorbing chromidia which cell has such a small amount of cytoplasm. Such a depression is followed in Protozoa by conjugation, but in the life of the germ-cells we do not know a process like that, therefore we must either suppose that the cytoplasm even then has the capacity of absorbing as much chromidia as is sufficient to improve the nucleo-plasmic ratio at least to such a degree that the increased assimilation can begin, or there must occur another process which gives the first impulse to surmount the depression. In the spermatocytes of H. arbustorum, as I believe, such a process occurs, but I shall discuss this question later. G OLDSCHMIDT (33|. as is known, explained the origin of the chromidia from the hypothesis that originally every nucleus (amphinucleus) has two kinds of chromatin, viz., idiochromatin and trophochromatin, the former representing the hereditary substance of the cell, the latter being the directive factor of the other functions of it. The trophochromatin, or parts of it, get during increased function into the cytoplasm, and form their chromidia. This process may be observed in every strongly functioning cell, but it is mostly evident in the germ-cells. It is undoubtedly true that GOLDSCHMIDT'S hypothesis has some disputable points, but it is true as well that it gives — in connection with the hypothesis of depression of HERTWIG — a useful key to the understanding of some functions of the cell, viz., it makes understandable that tbe hereditary parts of the chromatin do not become annihilated when the chromatin of the nucleus after pachytene stage so strikingly diminishes.
