Horváth Géza (szerk.): A Magyar Természettudományi Múzeum évkönyve 8. (Budapest 1910)
Soós, L.: A Helix arbustorum hím csirasejtjének fejlődése
SPJ^ MIOGENESIS OF HELIX ARBUSTORUM. 315 differs, however, from it, since the chromatin of the spermatogonia and spermatocytes forms a united thread, on the contrary in the second spermatocytes more or less isolated chromatin masses are to be found, i. e. the chromatin does not form a reticulum. The secondary spermatocytes of //. pomatia f according to BOLLES LEE (10) and P ROWAZEK (98) always go through this stage, but BOLLES LEE emphasized the fact that though between the two maturation divisions a resting period is intercalated which is succeeded by a normal prophase, this resting period is, in comparison with the corresponding period of the ordinary division, reduced, being so to say its extract. According to TSCHASSOWNIKOW (120) the first maturation division in //. pomatia always is succeeded by a definite, perfect resting period. There is no doubt that we must regard this as the ordinary manner of maturation divisions in which a shorter or longer resting period is intercalated between them, and the one first mentioned is only an exception which can be concluded from the rarity of the microscopical figures showing it. But several animals and plants are known, the reduction divisions of which take place in the manner which is in H. arbustorum exceptional. In several plants, as I know from G RÉGOIRE'S paper (37) the second maturation division immediately succeeds the first (Convallaria : SCHNIEWIND-THIES, Tricyrtis : IKEDA, Pallavicinia : PARMER, MOORE). But, as a rule, the plants also have a tendancy to go before the second division into a short resting stage. Similar cases are knowrn also in animals. PLATNER (93) observed that the second maturation spindle can form before the cell has arrived at the anaphase. According to VOM RATH (99) in spermatogenesis of Gryllotalpa the second maturation division immediately follows the first without the nucleus being transformed into a resting nucleus. At other times, though a nuclear membrane arises, the nucleus does not become a resting nucleus, since the chromosomes preserve their independence ( Ascaris : B RAUER ). Again in other cases a definite resting period separates the maturation divisions (rat: L ENHOSSÉK, E BNER; Scolopendra : BLACKMAN; Gonionemus: BIGELOW, etc., etc.). BOLLES LEE (10) tried to refute PLATNER'S and VOM BATH'S statements, but my observation made in H. arbustorum shows that the second maturation spindle can form before the cell reaches the telophase. The first phases of the division of the second spermatocytes in the case when it was preceded by a resting period, I have not had the opportunity of observing. According to BOLLES LEE (10) the outlines of the chromosomes of H. pomatia preparing to division become sharper and smooth, and then more chromatic than formerly. In a slightly
