Sequences in the maturation of the genitalia inTetrabothrius erostris(Loennberg, 1889) from the intestine ofLarus argentatus argentatusPontoppidan

Abstract

1. A detailed description, with illustrations, is given, of the sequences in development and maturation of the genitalia inTetrabothrius erostris.This is the first such account of any member of the new order Tetrabothridea.2. The effect of the very marked protandry on the form of the remainder of the genitalia is discussed.3. Attention is drawn to the unusual ovary which produces sclerotin and which it is proposed to call a ‘calycal-ovarium’.4. Comparison is made of the embryophore with that of the Cyclophyllidea. There is a suggestion that the embryophore may be formed of sclerotin inT. erostris.5. Par-uterine vesicles have been described for the first time in any member of the Tetrabothridea. These vesicles arise from the uterine primordium and have previously been confused with testes.6. The complex affinities of the order Tetrabothridea are discussed and some support arises for the creation of this new order.