Post-Reductional Meiosis: Its Mechanism and Causes

Abstract

The present paper was in proof when two other examples of diffuse centromeres or polycentric chromosomes were reported in the very recent literature, again in the class of Insecta (orders of Anoplura and Mallophaga). K. Bayreuther [1955, « Holokinetische Chromosomen bei Haematopinus suis (Anoplura, Haematopinldae »), Chromosoma 7: 260–270, 1955] observed the diffuse centromere during an investigation of the spermatogenesis of Haematopinus suis, n = 5, (class Insecta, order Anoplura). By X-rays treatment Bayreutheb obtained proof that the regular mitotic cycle takes place for chromosome fragments induced by the irradiation. Meiosis probably follows the post-reductional scheme, however the lack of any heteromorphous bivalent and the uniform tetrapartite structure of all five bivalents preclude certainty regarding the actual occurrence of post-reduction. A type of spermatogenesis very similar to that of Haematopinus has been reported by H. Scholl (1955, « Ein Beitrag zur kenntnis der Spermatogenese der Mallophagen », Chromosoma 7: 271–274, 1955) for Qyropus ovalis, n = 2, (class Insecta, order Mallophaga). Both Bayreuther (1955) and SCHÖLL (1955) use the expression holokinetic chromosomes « holokinetische Chromosomen ») Instead of polycentric chromosomes or diffuse centromeres.