The concept of the prophase of meiosis

The general outline of meiosis proposed by Wilson in 1925 included a diffuse stage following pachytene or early diplotene, although such a stage may be missing in some organisms. Different forms of such a stage are known to exist in male and female meiosis of many animals, but usually they are treated separately and not included as a special stage in the scheme of meiosis in modern textbooks. It was shown by a literature research that, up to 1940, the existence of a diffuse stage was recorded in meiosis of many plants (the sectioning technique used at this time made it easy to follow accurately the sequence of meiotic stages) but few authors considered this stage to be a common part of plant meiosis. Its existence was actually observed by many authors at this time, but it became a common tendency to regard it as due to “bad fixation”, or “fixation artefacts” only. Remarks about the existence of such a stage disappeared after the introduction of squash techniques, but started to reappear after 1960. Today, references about the existence of a diffuse stage are known from all groups of plants (Angiospermae, Gymnospermae, Pteridophyta, Bryophyta, Fungi, Algae). The conception of meiosis published by Wilson is thus found to be more close to reality and therefore it is proposed that such a concept is accepted as a general outline of meiosis.