The Opposition of Nautilus macromphalus. 467 



" The Oviposition of Nautilus macrompJialus" By ARTHUR 

 WILLEY, D.Sc., Balfour Student of the University of 

 Cambridge. Communicated by ALFRED NEWTON, M.A., 

 F.R.S., on behalf of the Managers of the Balfour Fund. 

 Received February 3, Read February 11, 1897. 



Nautilus macrompJialus is the species of nautilus characteristic of 

 the New Caledonian Archipelago, which comprises the islands of 

 New Caledonia, the Isle of Pines, and the Loyalty Group. I took up 

 my residence on the shores of Sandal Bay, Lifu, in August, 1896. 

 Having collected a number of Nautilus, I placed them in captivity in 

 a large native fish-trap, specially fitted up, fed them twice or three 

 times a week with fish, land-crabs, Palinurus, and Scyllarus, and on 

 December 5, 1896, commenced to obtain the fertilised ova. 



It is not necessary at present to describe the details of manipula- 

 tion, and I therefore proceed at once to give a brief account of the 

 more obvious features of the eggs as illustrated by the accompanying 

 figures. The eggs are laid singly and at night, in concealed situations, 

 and are firmly attached by a sponge-like reticulate area of attachment 

 placed towards their hinder inflated extremity, usually on one 

 face of the egg-case, but sometimes quite posteriorly, to a suitable 

 surface. I supplied the latter to the Nautilus by fixing pieces of old 

 sacking to the walls of the fish-basket, leaving loose, overhanging 

 folds, beneath which the eggs could be well concealed. The fibres 

 of the sacking were deftly employed by the Nautilus in cementing 

 their eggs. 



The ovum is enclosed within a double casing, an inner closed cap- 

 sule, and an outer capsule more or less freely open in front. The 

 material of which the capsules consist is of a bright milk-white 

 colour, and of firm cartilaginoid consistency. The capsules do not 

 collapse, but retain their shape when allowed to dry. 



For convenience of description, the exposed surface of the egg 

 may be spoken of as the dorsal or upper side, while the attached side 

 may be referred to as the lower or ventral side. The outer capsule is 

 separate from the inner capsule below and for about two-thirds of the 

 upper side, but is fused with it in the postero-dorsal region. Where 

 the two capsules are fused together the covering of the ovum is much 

 thickened. 



The egg with outer covering complete is of remarkably large size, 

 attaining a length of 45 mm., everything included, with a width of 

 16 mm., and a maximum height of 16'25 mm. The length and the 

 width are fairly constant in normally shaped eggs, but the height 

 varies somewhat, some eggs being a good deal flatter than others. 



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