The development of the trunk and tail lymphatics and posterior lymph hearts in anuran embryos

Abstract This paper represents the third part of a monograph on the development of the lymphatics and lymph hearts of Anura. In this part are considered the origin and development of the subvertebral, lateral, and dorsal lymphatics of the trunk, the caudal lymphatics, and the posterior lymph hearts. The chief lymphatic trunks arise along the veins from a series of small, spindle‐shaped, and discontinuous anlagen which subsequently coalesce and thus establish continuity with one another. Lymph plexuses are formed from which emerge the main secondary lymph channels. After such trunks are laid down as indicated, smaller branches and capillaries spring from them by sprouting or extension, due to their actively proliferating endothelium. The posterior lymph hearts ‘crystallize,’ so to speak, from localized areas of the lateral lymphatic plexus. During its reorganization and differentiation, it temporarily separates from the surrounding lymph plexus. Other genetic details, such as the formation of its valves, histogenesis of its walls, number of hearts laid down, etc., are also considered. Twenty‐two figures (microphotographs and reconstructions) accompany the text.