402 
NATURE 
[FEBRUARY 25, 1897 
THE EMBRYOLOGY OF THE NAUTILUS# 
NAUCTILOS macromphalus is the species of nautilus charac- 
teristic of the New Caledonian Archipelago, which com- 
prises 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 
manipulation, 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 ate 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 
capsule, 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 
Fic. 1.—Fertilised egg of Nautilus macromphalus in the natural attached 
position. The pectinate ridges and fenestrations, together with the 
slit in the wall of the outer capsule, are well seen. The arcuate thick- 
ening in the middle ofthe posterior half of the egg is due to the fusion 
of the outer with the inner capsule. In this ovum the anterior mem- 
branous prolongations of the outer capsule were unequal, the larger of 
them having the ferm of a thin flattened expansion. 
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. 
In Fig. 1 an egg is represented as seen in its usual natural 
attached position. The depressed or ‘‘ anterior” end of the 
€gg is, asa rule, directed vertically upwards. The outer cap- 
sule is continued in front-into two thin, translucent, terminal 
processes. For nearly half the length of the egg on the upper 
side the two halves of the outer capsules are separated by a 
narrow slit from one another and join together behind the 
1“ The Oviposition of Nautilus macromphalus.” By Arthur Willey, 
D.Sc., Balfour Student of the University of Cambridge. Communicated 
by Alfred Newton, F.R.S., on behalf of the Managers of the Balfour Fund. 
Received at the Royal Society February 3. Read February 11, 1897. 
NO. 1426, VOL. 55] 
centre of the egg. The dorsal ridge or suture of the inner cap- 
sule can be seen through this slit in the outer capsule. On the 
lower side of the egg the two halves of the outer capsule are 
continuous across the middle line throughout the length of the 
egg, except at the extreme anterior end. 
The surface of the egg in the posterior inflated region is 
smooth, with a few slight folds like the folds of drapery, giving 
it a graceful appearance. The anterior depressed region is 
characterised by the presence of a number of pectinate ridges 
and of fenestrations in the wall of the outer capsule (Figs. 1-3). 
Fic. 2.—The same egg from the side, showing the inflated posterior or 
proximal portion and the more flattened distal portion, as also the 
spongy area of attachment. 
Sometimes, however, the pectinations are obscure and the 
fenestrations may be absent. 
Hardly will any two eggs present an exactly similar appear- 
ance. Sometimes there are shred-like processes from the 
surface of the outer capsule, lending a more or less tattered 
appearance to the egg. 
In Fig. 4 another egg is shown with the above-described slit 
in the upper wall of the outer capsule, widened out so as to 
disclose the inner capsule to view. 
The inner capsule has a regular oval shape with anterior 
pointed extremity and a generally smooth surface. Its wall has 
a finely striated structure, the striz having a watery appearance. 
There are three distinct seams or sutures, representing lines of 
least resistance, in the wall of the inner capsule, namely, a 
median suture on the upper side (z.e. the side directed away 
from the attached side of the egg), and two lateral sutures 
placed towards the lower surface of the capsule (Figs. 4-6). 
The dorsal suture is marked by a prominent ridge which is 
produced in front beyond the anterior extremity of the main 
body of the inner capsule into a slender terminal appendix. 
The lateral sutures are marked by less prominent ridges, and 
Fic. 3.—The same egg as in the preceding figures, from below. Behind is 
the somewhat irregularly shaped spongy area of attachment. 
are continued into one another anteriorly, immediately behind 
the anterior extremity of the inner capsule. In consequence of 
the continuity of the lateral sutures, the lower side of the egg 
can be raised up like a cap or an operculum. The inner capsule 
is often easily ruptured along the sutures. In the middle line of 
the lower surface of the inner capsule there is a slight longi- 
tudinal groove, and other unimportant grooves often occur. 
Where the outer capsule is united to the inner capsule there is 
usually a depression or flattening in the wall of the latter. 
