

CEPB A LOI'ODA. 



ANATOMY. 

 ernal /'</////<>. 

 (Vphalopod inollusks an- immediately distinguished from all 



other classes of the mollusca by the circle of :icctalmla or nrins 

 which surrounds tlir head : these iu:iv be n-arded as homolo U -oii> 

 with tlu- loot of the irasteropods. witli its marir'nis produced into 

 theei^ht or ten proeees which are indifferently designated a> 

 arm*. acetabnhi or brachia. 'I'lu 1 extension of tliis inoditicMl l'o..t 

 :ii-oiin<l tlie niont h of tlie animal, its innnit'old uses in its eeunoniy 

 :ui(l its hio-h structural development. eonil>ine to place the 

 eej.halopoda at the head of the mollusc:!.* 



The mouth is supplied with a pair of calcareous or horny ja svs. 

 ivsemlilino- in form the Leaks of n i)iirrot. The arms proper, in 

 the naked cephalopods. are ei^ht in numlu-r. and are dist inct ively 

 ealled seile arms, to dist.iniruisli them from the tentacular arm> 

 or tentacles, much lon-vr, and capable of retraction within 

 pouches, which are additionally possessed l.y those specio which 

 have an internal shell or cuttle-hone. The sessile arms are pro- 

 vided with suckers or hooks for prehension, covering their 

 interior surface, whilst the tentacles an- expanded into clul. 

 shaped terminations similarly armed. In the tf autilu8, sole livin- 

 representative of an exceedingly numerous extinct order, the 

 arms drovm-rate into numerous tentacle-, unarmed, which arc 

 retractile into ei-ht sheaths, morphologically representing the 



Tin- nervous system :m<l l>hyl<>uvny of the -e|.l.aloi,,.la liave IHTII 



studir.l i.v Hennann v..n Jhering Leipzig, 1877), who states as a resiUI 

 ,f i,u researches .MHMI the hoinol,, u i-s of th.- ganglia and rierves, that the 



arms of the cephalopods in no waj represent thefooj i Uie gasteropoda, 



hut are t.-ntacular ,r r mvths of thrhca-l : tliat the only i-art ..I thecepbalO- 

 :in:ln..-(.ns to tlu- f..t of Ilie gBSteTOpod, 18 t!,r Siphon. 



