THE RELATIONSHIP BETWEEN THE PITUITARY GLAND AND THE GONADS IN FUNDULUS

¹ From the Thompson Biological Laboratory, Williams College, and the Marine Biological Laboratory, Woods Hole

Injections of pituitary extracts into male Fundulus have been practically without stimulating effect on the testis. In females records were obtained from thirty-five cases of which only four delivered eggs earlier than did control animals, one case delivering ripe eggs six weeks, the other three cases about four weeks before the normal breeding season.

After removing the pituitary gland the gonads undergo regressive changes as compared with the controls, changes which are particularly striking in the testis. When the pituitary gland was removed in the fall and the animals were allowed to run until the next breeding season in May and June the testes failed to enlarge as they normally do. Microscopically such testes showed numerous primary spermatogonia but very few spermatocytes and practically no spermatozoa. When the pituitary gland was removed in March and April, after the testis had already enlarged somewhat, fourteen to twenty-one days after operation the testes had become notably smaller than in control animals, and showed only primary spermatogonia with a few spermatids and spermatozoa. These results indicate that the pituitary gland exerts a controlling influence on the seasonal cycle which the testis of this teleost fish exhibits. This influence is apparently of greater importance in maturation than in proliferation of the germ cells.