[Development of the gonads and gonaducts in the polypterids (Pisces)]

No study of the development of the gonads and gonoducts in Polypterus has ever been made in a more or less complete way. The present study does not fill up this gap, but repairs several lacks of knowledge, by putting clear a few items that may contribute to a better understanding of this development. In larvae between 5,5 mm and 9,6 mm the primary gonocytes appear under the pronephric ducts in the anterior region of the opisthonephros. A genital crest is foreshadowed there; one of its characteristics is a cubial epithelium. The latter does not have any relation with peritoneal channels and it does not contribute to the formation of gonocytes. In the following stages the gonocytes get very numerous because of cellular multiplication. They cause a local transformation of the genital crest into a genital fold; when the number of gonocytes has increased very much, a part of the fold gets transformated into a gonad. At no stage is there any intrusion of medullary tissue into this gonad anlage.