Morphologie abdominale des machilides (thysanura)—III. Squelette et musculature des segments génitaux mâles et des segments postgénitaux

Abstract

This paper, which ends my study on the machilid abdomen, contains a detailed description of the male genital (VIII and IX) and postgenital (X and XI) segments. The VlIIth segment is slightly modified compared to the pregenital segments; in particular, the sternite remains rather large. The more-reduced IXth sternite is still present; there is also a pair of transverse sclerites (“sclérites en S”) detached from the anterior part of the coxites. Lying under the large IXth coxites is the genital chamber containing the phallic complex. In the most complete cases, this complex comprises 2 pairs of parameres and the penis. The parameres, attached to the inner face of the VIIIth and IXth coxites, are homologous to the female gonapophyscs and serially homologous to the eversible vesicles of the pregenital segments. Therefore, they are considered as coxalia interna. The penis, for which no corresponding formation can be found in the female, is composed of a phallobase and an aedeagus; it is attached to the ventral part of the IXth segment, just behind the IXth parameres which are united at their base. The anatomy suggests to us that the penis is formed by the union of 2 coxalia interna mediales, belonging to the IXth segment; but according to some embryological observations, it is formed as a result of the migration and union of the appendicular outgrowths of the IXth segment. The ventral part of the Xth segment is much reduced, and no trace of sternite or coxites is to be found. However, the ventral part of the Xlth segment presents a pair of flattened lobes, the paraprocts, which I consider as the XIth coxites; but for embryologists these lobes are subanal plates belonging to the telson. This latter is only to be recognized by the presence of a small subanal lobe.