Horváth Géza (szerk.): A Magyar Természettudományi Múzeum évkönyve 8. (Budapest 1910)
Soós, L.: A Helix arbustorum hím csirasejtjének fejlődése
SPJ^ MIOGENESIS OF HELIX ARBUSTORUM. 323 This explanation agrees with that given by B RAUER (1/) of the reduction of Ascaris megalocephala. * The growth period of the spermatocytes of H. arbustorum can be divided into two parts characterized by the processes which take place during transformation of the cytoplasm, and chiefly by those taking place during transformation of the chromosomes. The first part lasts till the formation of the bouquet, the second begins when the chromosomes become scattered through the nucleus. The cell increases during the first part in a less degree; the increase is limited almost to the nucleus, but the real increase takes place during the second part of the growth period. The chromatin is divided first into chromomeres suspended in the linin network which gradually unite, to form thin threads. The thread divides afterwards into thicker, U-shaped, split chromosomes. The development of the chromatin agrees till that stage with that of the chromosomes of the somatic cells. The splitting of the chromosomes is followed, as a rule, by the formation of the spindle and the division itself, and variation can be found only in the duration of the time during which the thread-like chromosomes transform themselves into the rod-shaped, ovoidal, or spherical chromosomes of the spindle. The development of the chromosomes of the spermatocytes of If. arbustorum differs from this scheme, since they do not transform themselves after splitting into the definite chromosomes of the spindle, but lose their independence, and dissolve into chromomeres which become equally scattered through the linin network developed in the mean-time. The constitution of the nucleus in this stage is very similar to that of the resting spermatocytes, and thus we may say that the nucleus became again a resting one without preceding division, used the term «resting« in morphological, and not in physiological sense. Similar phenomena have also been observed by former authors, but chiefly in ovogenesis. According to WINIWARTER (128) in ovogenesis of Mammals (man and rabbit) the same two periods are to be distinguished as in spermatogenesis ot //. arbustorum. Two similar, but not so sharply determined parts are to be observed in ovogenesis of Amphibia (CARNOY and L EBRUN), Triton (LUBOSCH), and Selcuhii. Amongst Invertebrates SCHOKAERT (108) in Pohjclada (Tliysanozoon Brocchii), BONNEVIE (13, 14) in Enteroxenos, STSCHELKANOWZEW (118) in Aphis, GOLDSCHMIDT (34) in Dicrocoelium lanceatum. WOLTERECK» 129)and S CHLE]P (107) ÍII OMracoda (the latter author in Notodromas monacha and Cypris ovum), POPOFF (94) in I'aludina observed an intercalated resting stage (all these authors 21*
