ANATOMY OF NAtJTILUS POMPILIUS. 



43 



transversely so as to present a median zigzag elevation. The 

 funnel-shaped membranous process above noticed is continuous 

 with the lining membrane, consisting of an extension of the same 

 epithelial pavement ; but the cells are somewhat larger and more 

 regular in form. The cavity of each follicle, therefore, communi- 

 cates with the exterior through the centre of this process ; and the 

 aperture is thus guarded by a kind of circular valve, permitting 

 the escape of secreted matter, but effectually preventing the 

 entrance of fluid from without." 



In his fig. 9, pi. XV., Mr. Macdonald depicts certain " crystal- 

 line bodies often occurring within the follicles." 



From what Mr, Macdonald states, one would be led to conclude 

 that all the follicles have the same structure ; but I suspect this 

 to be an oversight. 



In the second edition of Professor Owen's Lectures on the 

 Invertebrata (1855), I find no mention of Valenciennes' discovery 



Nautilus pompilius. Fig. 1. 



Viewed from the left side and a little behind. 



Two of the anterior chambers, and the fifth or posterior chamber, laid open. 

 Natural size. 



a. Shell muscle, b. Ovary, e. Intestine, d. Heart ; d'. its pyriform appendage. 

 e. Superior anterior chamber ; e'. its foUicles. /. Inferior anterior chamber ; 

 /'. its follicles, ff. Posterior chamber ; ^'. FoUicles. h. Cut ends of bran- 

 chial arteries, i. Teimination of vena cava. k. Pallio-visceral ligament. 



