Abstract
Department of Biology, Boston University, Boston, Massachusetts 02215, U.S.A. (Received 9 January 1978) Selective ablation of portions of the pituitary gland (Dodd, Evennett & Goddard, 1960) and indirect evidence from heterologous immunohistochemical (Mellinger & Dubois, 1973) or radioimmunoassay (Scanes, Follett & Goos, 1972) data has indicated that the anatomically discrete ventral lobe of the elasmobranch pituitary gland may be the sole source of gonadotrophins in these fishes. Bioassay studies have, however, given conflicting results. With a bioassay involving the uptake of 32P by the testes of 1-day-old chicks, Scanes, Dobson, Follett & Dodd (1972) found gonadotrophic activity only in the ventral lobe, whereas Firth & Vollrath (1973) showed gonadotrophic activity in both the ventral and median lobes of the pituitary gland of Scyliorhinus canicula when using the Xenopus oocyte meiosis assay. Thus there is still no agreement as to the nature and source of the gonadotrophin(s) in elasmobranchs. The dispersed

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