Horváth Géza (szerk.): A Magyar Természettudományi Múzeum évkönyve 8. (Budapest 1910)
Soós, L.: A Helix arbustorum hím csirasejtjének fejlődése
SP J^MIOGENES IS OF HELIX A RBUSTORUM. 321 growth period forms thin threads which afterwards arrange themselves parallel to one another, and in the next stage the thin threads become transformed into thick ones. These latter are said to arise through the side-to-side union of two thin threads. It is evident that the evidences are fairly poor, and are not in proportion to the number of the investigations made. Since the process of union has not yet been observed in living material its proceeding can be concluded only by the seriation of the microscopical figures, therefore the correct explanation depends upon the correct seriation. To be mistaken in this respect is very easy, and one of the opponents of the hypothesis, MEVES (72), really led back its origin to incorrect seriation. According to him not the thick threads arise through conjugation of the thin ones, but the thin threads originate by the splitting of the thick ones, i. e., the pachytene nucleus is older than the leptotene. In II. arbuatorum the leptotene nucleus is certainly older than the pachytene, so I must conclude, upon base of an analogy, that the direction of development passes from the thin threads towards the thick ones, and therefore, though in some cases the pachytene nucleus is older than the leptotene one (Salamandra ), this cannot be regarded as a sufficient ground upon which to refute the hypothesis. More important in this respect are the observations of POPOFF (94) made in ovocytes of Paludina, and those of G OLDSCHMIDT (34) referring to Dierocoelium lanceatum. The chromatin of the ovocytes of these animals first forms thin threads (leptotene nucleus) which become afterwards thicker and shorter. The threads are split very early at the beginning of thickening. They become yet thicker in the next stage, their number becomes smaller, and their split remains constantly as sharp as it was in the beginning. It is very important that they never coalesce perfectly. — In these two cases the thickening of the chromatin threads can be followed from step to step (cf. P OPOFF , Pl. IV., Figs. 24—31., G OLDSCHMIDT , Pl. VII., Figs. 5—9.), but the reciprocal position of the two threads constituting the thick thread always remains the same. — This phenomenon cannot be interpreted otherwise than in the conception of FLEMMING and MEVES, according to whom the thread is already split in the early spireme, even if it be then invisible, i. e., the split is prefoimed in the thread — as FLEMMING expressed himself — and means nothing rise than a preparation to the next division. It is very important, as regards the question, that not only germ-cells, but also somatic cells may bave split chromatin threads [connective tissue and endothelium cells of Salamandra, according to FLF.MMING I29)~. Not less important Annales M us ei Nationalis Hungarici. VIII. 21
