Fridericia Species Research Articles

Altitude and Animal Development

SOME time ago I found in the alluvium of a little Derbyshire stream a tubifioid of a species and genus new to Britain. It was characterised by its large lymph corpuscles and its Pachydrilus-like form, on which account it was named Meganympha pachydriloides. Friend. The description showed that the animal possessed an average of forty-five segments, three or four forked setas like Limnodrilus, a brain deeply lobed behind, spermathecae pear-shaped or globular, and a penis-sheath, or large penial seta. While working out some species of Fridericia a few days ago, and turning to Bretscher (Revue Suisse de Zoologie, 1901) for some details, my attention was directed to his description of Rhyacodrilus falciformis, and it appeared evident that the Derbyshire worm was one with the Swiss.1 But Bretscher states that the alpine forms have only thirty segments. Issel, de Ribaucourt, and Bretscher have recently given us many facts to show that annelids of the same species are very much smaller when found high up in the Alps than when found in the valleys. The foregoing seems to be an interesting confirmation of these statements.