NAUTILUS. 



383 



and that of our type. For it is only the female Argonaut 

 which bears a shell ; it is not chambered, and is a shelter for 

 the eggs — a cradle, not a house. It is usually stated to be 



Fig. 168. — The Pearly Nautilus (Xniililus pompilius). 

 — After Owen. 



The shell is represented in section, but the animal is not dissected. 

 c, Last or body-chamber, separated by a septum (se.) from the 

 compartment behind; $., the siphuncle traversing all the 

 compartments ; ?«., the portion of the mantle which is reflected 

 over the shell; h., the- hood ; e., the eye with its opening to 

 the exterior; /., the lobes which bear the sheathed tentacles 

 (i.) ; sz. t the incomplete siphon ; ;««., the shell muscle ; «., the 

 position of the nidamental gland. 



formed by two of the arms, but it seems doubtful whether it 

 is not in reality due to the activity of the mantle. 



It is instructive also to compare the Nautilus shell with 

 that of some Gasteropods, for there also chambers may be 

 formed. But these arise from secondary alterations of an 

 originally continuous spiral, and the resemblance is never 



