The Tetrads in Apoda (Amphibia)

Abstract

WORKERS on urodelan spermatogenesis have reported the occurrence of large multiple rings in the first maturation divisions of the animals of that group. These multiple rings form the most conspicuous of the tetrads in practically every urodele studied. Multiple ring tetrads in Anura are very rare, and are practically confined to some members of the Discoglossidæ (Alytes obstetricans Janssens and Willems¹: Bombina pachypus Galgano²: Bombina orientalis Sato³). Swingle⁴ reported such multiple ring tetrads in the male sexual cycle of the tadpoles of Rana catesbiana of 40–60 mm. length, while in the second larval sexual cycle of this animal the typical anuran kind of tetrads (simple rings) were present. Swingle, and later Iriki⁵, advanced the view that the multiple ring tetrad must be regarded as the ancestral type of tetrad in Amphibia and this view has been further emphasized recently by Sato³, who has found such compound tetrads in Bombina orientalis.