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

In 1900 Prof. J. Graham Kerr published the results of his investigations into the habits and reproduction of Lepidosiren in the swamps of the Gran Chaco, in Paraguay (' Phil. Trans.,' Series B, vol. 292). He found that just before the breeding season papillæ which occur on the pelvic limbs of the male rapidly develop into long, bright-red, vascular filaments. These persist throughout the breeding period, during which the male fish remains in the Nesting burrow with the eggs and larvæ. After this period the filaments disappear, by atrophy of the tissues and disintegration, not by absorption. Neither filaments nor papillæ usually occur on the pelvic Iimbs of the female, but papillæ in a very rudimentary condition occur occasionally in female specimens, and, judging from the analogy of sex-limited characters in other vertebrates these specimens are possibly the oldest, and perhaps no longer fertile. Prof. Graham Kerr discusses the question of the function of these vascular filaments in the male. Sir Ray Lankester had suggested that they were accessory organs of respiration; Dr. Hans Gadow that they might be spawning brushes tor spreading the semen; Graham Kerr himself thought they might be due to "the intense vital activity associated with reproduction," but on further consideration agreed with Sir Ray Lankester that respiration was their most probable function.