La partenogenesi negli Afidi

Abstract A comparative study of the parthienogenetic and amphigonic egg development of Aphids, has shown & clear resemblance between some aspects of the two maturative processes. In the amphigonie egg bivalents become indistinet soon after the stage of highest contraction. In the parthenogenetie egg however the bivalents the stae of highest contraction. In the parthenogenetie egg however the bivalents separate and the diploid number of chromosomes is restored within the nuelear membrane. The second maturative division originates, in the partheogenetic egg a single diploid polar body. In the amphigoni egg the emission of two aploid polar bodies occurs in the normal way. In both ovogenetic processes the bivalents reach threfore the highest contraction stage before the «resting» stage. A delay in the beginning of the resting stage of the nucleus is shown therefore in the egg maturation of Aphids, which is not shown in most other Inscets orders. Such peeculiar behaiour of the chromosomes of the amphigonic egg...