The vascular filaments on the pelvic limbs of Lepidosiren, their function and evolutionary significance

Abstract

In 1912 it was suggested by the author that the water in the nest-burrow, in which the eggs and larvae were guarded by the [male] Lepidosiren, was deficient in O, and that the function of the pelvic filaments which are developed only in the [male] and only in the breeding season was to give out O for the respiration of the eggs and larvae, the parent being provided with lungs which can be filled with air by visits to the surface. In 1926-27 G. S. Carter investigated the swamps in Paraguay where Lepidosiren lives, and proved experimentally that the water below the surface is almost entirely destitute of O; he independently formed the same conclusion concerning the function of the pelvic filaments of the [male] Being unable to experiment on Lepidosiren itself the author made experiments to ascertain whether O was given off by other fishes and by axolotls when placed in water artificially deoxygen-ated. Positive results were obtained by placing the animals in decolorized methylene blue, the restoration of the color proving that O was emitted. The author suggests that the passage of O from the blood-vessels through the tissues was itself the stimulus to vascular hypertrophy which on the Lamarckian theory caused the evolution of the filaments.