V. On the structure of the chorda dorsalis of the plagiostomes and some other fishes, and on the relation of its proper sheath to the development of the vertebræ

I take the liberty to present to the Royal Society the results of an extended series of investigations into the development of the vertebræ of the plagiostomous and some other fishes. The chorda dorsalis of the Plagiostomes, ofChimœra, Acipenser, Scaphirhynchus, Toxodon , andLepidosiren , showsfour distinct parts, viz.— 1st. Theouter elastic membrane , a homogeneous elastic coat, which is not unfrequently perforated with holes of different sizes, of the same kind as those of the fenestrated membrane of Henle. 2nd. Theproper sheath , formed of connective tissue of fibrous appearance, and generally provided with many plasm-cells.