II. On the development of the spinal nerves in elasmobranch fishes

Abstract

In the course of an inquiry into the development of Elasmobranch Fishes, my attention has recently been specially directed to the first appearance and early stages of the spinal nerves, and I have been led to results which differ so materially from those of former investigators that I venture at once to lay them before the Society. I have employed in my investigations embryos of Scyllium canicula, Scyllium stellare, Pristiurus , and Torpedo . The embryos of the latter animal, especially those hardened in osmic acid, have proved by far the most favourable for my purpose, though, as will be seen from the sequel, I have been able to confirm the majority of my conclusions on embryos of all the above-mentioned genera. A great part of my work was done at the Zoological Station founded by Dr. Dohrn at Naples; and I have to thank both Dr. Doiirn and Dr. Eisig for the uniformly obliging manner in which they have met my requirements for investigation. I have more recently been able to fill up a number of lacunæ in my observations by the study of embryos bred in the Brighton Aquarium; for these I am indebted to the liberality of Mr. Lee and the Directors of that institution.