No. 3-] THE ANATOMY OF NAUTILUS POMPILIUS. 153 



3 



potash no change occurred, either in the shape of the mass or 

 in its hardness. Drawings were made of the masses before 

 treatment, and with these the masses were afterwards com- 

 pared. But the crystals were 

 broken clown, according to the 

 well-known action of caustic pot- 

 ash upon calcium carbonate. This 

 experiment tends to prove that 

 the crystals were not cemented 

 together after the death of the 

 Nautilus by the coagulation by 

 alcohol of some fluid in which the 

 crystals normally are immersed. 

 Upon treating the masses with 

 dilute sulphuric acid they were 

 broken down, and characteristic 

 crystals of selenite were formed. 

 If these masses which I find in 

 the otocysts were produced by 

 coagulation processes they would 

 neither be so regular in shape as 

 they are, nor solid, but would 

 abound in cavities filled with a co- 

 agulate. In only one case have I 

 found any organic matter with 

 these masses, and in this the 

 quantity was very small and the 



FIG. 4. A section of the salivary gland 



material was found as a thin layer of Nautilus pompilius. outlined with the 



, i .- r , , camera lucida. 



upon the outside of the mass. 



From these considerations I judge that the otolith of Nautilus 



pompilius is single. 



THE PALLIAL COMPLEX. 



The pallial complex of Nautilus pompilius presents several 

 points in which it differs from that of other Cephalopoda. 

 The mantle cavity extends completely around the body. It is 

 deepest ventrally and shallowest at the sides, and about a third 

 as deep dorsally as ventrally. The gills are four in number, 



