Horváth Géza (szerk.): A Magyar Természettudományi Múzeum évkönyve 8. (Budapest 1910)
Soós, L.: A Helix arbustorum hím csirasejtjének fejlődése
SPJ^ MIOGENESIS OF HELIX ARBUSTORUM. 319 4. The reduction. The reduction of Helix was first studied by PLATNER (93). According to him the reduction takes place by the telophase of the first maturation division remaining out, and the chromosomes arranging themselves, without going into resting stage, in the equatorial plate of the second maturation spindle which has formed in the mean-time. The halves of the chromosomes pass into different daughter cells, i. e. into the secondary spermatocytes which then have half as many chromosomes as the primary spermatocytes. According to VOM RATH (99) the reduction of Helix agrees with that of Gryllotalpa, i. e. its chromatin masses into 12 tetrads the constituent parts of which pass during the reduction period into four different daughter cells which have then he reduced number (=12) of chromosomes. In Helix, as mentioned above, no tetrads arise, and if its spermatocytes have tetradlike bodies they cannot be identified with the true tetrads, especially with those of the Arthropoda. Becent investigators have shown that the results of VOM BATH have only the value of a scheme, and also his figures are in the highest degree diagrammatic, therefore his investigations are not so important in the question of reduction as formerly believed. Neither former investigators, nor the present author has found in Helix such microscopical figures as are similar to those given by VOM RATH from Gryllotalpa. VOM RATH'S views exercised great influence also upon those of P ROWAZEK (98). The chromatin of Helix — according to this latter author — mass themselves into 12 chromosomes, or 12 chromosome groups, which represent tetrads. The constituents parts of the tetrads are rarely to be seen, and mostly only two parts are distinctly visible which are coalesced either at .their ends, or in the middle, and thus arise x-, or o-shaped bodies. The tetrads divide during the maturation divisions into four parts, viz. in the first division longitudinally, in the second «apparently» transversely and thus get the four spermatids 12 chromosomes, which is equal to their reduced number. BOLLES LEE'S investigations (10) gave a quite different result. The spermatogonia of Helix pomatia — according to this author — have 21- chromosomes, and so many have also the primary spermatocytes. The chromosomes of the spermatocytes are ovoidal, and divide in the first maturation division transversely, thus the secondary spermatocytes have also 24 chromosomes. The second maturation division takes place in quite the same manner as the first, therefore the number of the chromosomes does not become reduced at all.
