STAGES IN THE DEVELOPMENT OF THE PICKED OR SPINY DOGFISH, SQUALUS ACANTHIAS LINN

¹ Government Marine Biologist and Director of Fisheries, Union of South Africa

1. Squalus acanthias is an ovoviviparous dogfish with a wide range of distribution.

2. The male and female reproductive systems, especially the internal structure and the closing device of the uterus, are described.

3. Oviparous development takes place in a thin transparent egg capsule, different from the usual Selachian egg capsules, up to a certain stage, when the capsule ruptures and then the development becomes viviparous.

4. Embryos at different stages of development are described. Some capsules contained single embryos, others twins and still another triplets.

5. The functions of the external gills are dealt with, it being concluded that their function is primarily respiratory.

6. The vitelline circulation is described.