ON NAUTILUS AND SOME OTHER ORGANISMS. 147 
“On the bottom,” says Rumphius, according to Moseley’s 
translation, “the animal creeps with the other side! upper- 
most, with the head and tentacles on the bottom, and makes 
tolerably fast progress.” The only comment I can make on 
this statement is that it is inconceivable. I wish'I had the 
work of Rumphius to refer to, in order to find out how he 
succeeded in seeing the Nautilus at all on the bottom. He 
goes on to say, “The animals remain mostly at the bottom, 
creeping sometimes into hoop-nets set for fish and lobster-pots ; 
but after a storm, when the weather becomes calm, they are 
to be seen floating in troops on the surface of the water... . 
The floating, however, does not last long, for, drawing in all 
their tentacles, the animals turn their boats over and go down 
again to the bottom.” 
The Nautilus can no more turn its boat over than a suc- 
cessful balloon ascent can end by the cage coming down 
uppermost. Anyone can convince himself of this by placing 
an empty Nautilus shell in water. A remarkably small weight 
is sufficient to sink such an empty shell; and when the living 
animal retracts itself and ceases all muscular action, thereby 
converting itself, as it were, into a dead weight, it is heavy 
enough to sink several shells in addition to its own. 
There is a slight error in Moseley’s account of the move- 
ments of the Nautilus, which may as well be corrected. He 
says, ‘On either side of the base of the membranous opercu- 
lum-like headfold . . . the fold of the mantle closing the 
gill-cavity was to be seen rising and falling, with a regular 
pulsating motion, as the animal in breathing took in the 
water, to be expelled by the siphon.” It is not a fold of the 
mantle which is thus seen to pulsate, but the posterior free 
membrane-like expansion of the funnel on either side. 
Besides observing the movements of the Nautilus inthe narrow 
limits of jars and buckets, I have also placed them in the sea in 
shallow water, and will briefly describe one such experiment. 
On March 16th a Kanaka brought me six Nautili. All of 
them sank to the bottom of the buckets except one, which 
1 That is, the ventral side. 
