Horváth Géza (szerk.): A Magyar Természettudományi Múzeum évkönyve 8. (Budapest 1910)
Soós, L.: A Helix arbustorum hím csirasejtjének fejlődése
306 D E L. SOÓS neous, because tbe nuclei of ibe spermatogonia and those of the basecells lie originally in the same ground substance. The cytoplasm of the base-cells can be easily distinguished later, in which the spermatogonia cannot be imbedded in consequence of its poverty. A part of the cytoplasm surrounding the nucleus later differentiates. The nuclei afterwards pass out of the common plasm, and seize the cytoplasm differentiated around them, thus originate cells having a typical constitution. The division of the spermatogonia is to be seen on Figs. 3—7., Pl. VII. I remark by the way that in follicles in which the spermatozoa are abundantly developing, only few cells in division are to be found, from which we can conclude that their chief division period lies in a former stage of development. As the nucleus of a spermatogonium prepares for division, its chromatin resolves itself into a spireme, consisting of thin threads (Pl. VII., Fig. 3.). The threads shorten and thicken afterwards, and transform themselves into short and thick, arcuated chromosomes (Pl. VII.. Fig. 4.), which afterwards become still shorter, spherical or ovoidal (Pl. VII., Figs. 5—6.), and then arrange themselves in the equatorial plate. We find then the number of the chromosomes approximate to 48, which number is equal to that found by ANCEL in the «large germ-cells». The true number of chromosomes can be scarcely determined, because they are crowded in relatively small cells, but it is certainly greater than 40. Former investigators (PLATNER, BOLLES LEE, PROWAZEK ) stated the number to be 24, and it was only shown by ANCEL that the true number is 48, which agrees with the number found in the first blastomeres, therefore it must be their normal number. According to ANCEL this normal number can be found only in the «large germ-cells» — the mother cells of the spermatogonia — which number in the first phases of division become reduced to 24, i. e., the reduction takes place in the spermatogonia. The cromosomes of the spermatogonia of H. arbustorum, however, are certainly not reduced, therefore the reduction must take place in a later stage of development. It seems to me quite indubitable that even the number of the chromosomes of H. pomati« does not become reduced in the spermatogonia, but the reduction of this species is like that of IL arbustorum . My conclusion is based upon the fact that the mode of reduction of H. arbustorum lias — according to my observations — a general value in Pulmonates. ANCEL'S error was due to the circumstance that he — as can be seen from his figures — could not precisely distinguish the spermatogonia from the first spermatocytes, and regarded
