824 THE AMERICAN NATURALIST. [Vor. XXXV. 
bi-weekly ; at Manjuyod, on the other hand, visits to the 
cages are made at irregular intervals. The bait is then 
renewed, the captured fish removed, — this through a trap- 
door in the bottom, — and the apparatus sunk again to the 
bottom. | 
In the accompanying cut (Fig. 1) I have attempted to repre- 
sent a bo-bo in position, with Nautilus in and around it. This, 
I believe, gives a moderately accurate idea of some of the posi- 
tions assumed by the animals. Several are represented, partly 
A B 
Fic. 4, A and B.— Diagrams of shells showing in stippled areas the oral apertures of 
ale (A) and female (B) Nautilus 
retracted, in a position of rest, and one of them, attracted by 
the bait, is shown swimming rapidly near the bottom some- 
what in the direction of the cage. The degree of shadow is, of 
course, hypothetical, and it is doubtful whether the bottom 1$ 
as free from other living forms as I have indicated. 
The Shell. — In examining fresh specimens I notic 
there appeared to be sexual differences in the shells. That of 
the female was wider at the sides of the oval aperture and here 
showed a somewhat angular contour. This peculiarity Lhar 
expressed in the accompanying Fig. 4, B, and it may be con- 
trasted with the condition of the shell of a male shown in the 
ed that 
