r, TIIM SKIN. 



typical ei^ht arms. In this animal only, the body is contained 



within, niiil protected by. :in external shell. Avhich compensate^ 

 to it the hiss of oHensive and locomotive power possessed by its 

 inoiv highly ornani/.ed allic>. 



rehind the arms, the circle of which may constitute- its crown, 

 that major portion of the In'ud is situated which is usually dis- 

 tinct ivelv sn designated : its dorsal aspect exhibits on either side 

 :in i-i/c. The head may be joined to the body by a more or less 

 const ricted /</, . or is frc<|ncntly sessile upon the latter, without 

 intervening constriction. The body, or mantle, is dorsally more 

 or less continuous with the head, but vent rally forms a sack 

 anteriorly opui. and from which emeroes the /'//////r/ ni 1 .s-////o// 

 'which ma\ also be regarded as a modification of a portion of the 

 foot of tlie Li'Msteropoda I. 'I'he sack or body is. in a small portion 

 of the octopod and in t he decapod species, expanded intoposlero- 

 lateral membranes, possessing the power of und nlat or\ motion, 

 and which may be considered as t he equivalent of tin*, in func- 

 tion. though not in appearance. 



The SHn. 



The epithelium in the dibranchiate eeplinlopods. is comjtosed 

 of flask-like or rounded "-rain-like cells; tbey Are cylindrical in 



the Nautilus. I'nder this lies a thin fibrous layer, which a^ain 

 OOVera that eontainin- the chroniMlo|>hores. r |1ie skin of the 

 cephalopod. |art icula rly its dorsal surface, is covered with 

 apparently minute specks of a dark reddish color, which are, in 

 reality, the pioment cells or chroma tophores ( I'l. \-2, f. S, 11): these 

 each provide.l with radiating muscles, by which, at the will 

 ..f the animal, the little sacks are "Teal ly dilated, and the color 

 becomes intensified. The rapid chameleon-like changes of color 

 peculiar to the cephalopoda anioiii; niolliisca. are thus produced : 

 whilst the aeeompan\ in-' opal-like and silvery appearance ex- 

 hibited by the cuttle-fishes, is dm- to a thin layer nnderlvino- the 

 pi-iiient layer. : md rellectin- throii-h it. In the tentacles of 

 Naulilu>are found ej.it helial pi-'meiit cells, which, accordin- to 

 Knniphins. are used >imilai-|y to the chromatophores. 



The outer >kin, in many of the -enera. is furnished with con- 

 tractile tubercular elevations or /,<v//v/.s. which are raised when 



