a. Shell muscle. b. Ovary. c. Intestine. d. Heart; d'. its pyriform appendage. e. Superior anterior chamber; e'. its follicles. f. Inferior anterior chamber; f'. its follicles. g. Posterior chamber; g'. Follicles. h. Cut ends of branchial arteries. i. Termination of vena cava. k. Pallio-visceral ligament.
In the second edition of Professor Owen's Lectures on the Invertebrata (1855), I find no mention of Valenciennes' discovery of the additional four apertures; but the author states that "on each side, at the roots of the anterior branchiæ, there is a small mamillary eminence with a transverse slit, which conducts from the branchial cavity to one of the compartments of the pericardium containing two clusters of venous glands. There are also two similar, but smaller, slits, contiguous to one another, near the root of the posterior branchia on each side, which lead to and may admit sea-water into the compartments containing the posterior cluster of the venous follicles." In this work the ovary is not only described, but figured, on the right side of the gizzard. The figure, however, rightly places the greater part of the ovary below that organ.
Nautilus pompilius. Fig. 2.
Natural Size.
The pallio-visceral ligament seen from below: torn on the right side to show the rectum and oviduct; cut through on the left side along the dotted line close to d' in the preceding figure.
a. Anus. b. Oviducal aperture. c. Heart. d. Left branchial veins. e. Right branchial veins. f. Oviduct cut through. g. Ovary. h. Rectum. i. Mantle. k k k. Pallio-visceral ligament; k'. its torn portion. The oval "aperture for the siphonal artery" is seen to the left of c', and the right-hand style in Fig. 1 passes through it.
On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection. By Charles Darwin, Esq., F.R.S., F.L.S., & F.G.S., and Alfred Wallace, Esq. Communicated by Sir Charles Lyell, F.R.S., F.L.S., and J. D. Hooker, Esq., M.D., V.P.R.S., F.L.S., &c.