210 INVEKTKliliATK ANIMALS. 



the beak of a liinl (tii,'. 14i) «< !, t(jg\'tlier M-itli an " oilontophore " 

 or "tongue," the himlev ))ait of Avliieh is fuiiiislied with recurved 

 spines. Tliis cavity Ic.-nls liy a Q-ullet, furni.slied witli salivar}' glands, 

 into a stnni:icli, friiin which an intestine is continued to terminate by 

 a disti]ict aims, wliicli nin'os mi the vcnti:il surface at the base of tlie 

 so-called "funnel." 'J'lie funnel is a njuscular tube jibiced on the 

 inider surf ice i>f the licad, and coninumicaling mi the ime hand witli 

 the extern.'il medium, and nn the iitlier with the c.nity uf the nrintle. 

 In tlie ynntiliix alone it is simjily binned of iv,\> nnr-cular lubes, 

 which are in a]i|Misitiiin, but are nut united tui^etlier so as to form a 

 tulie. In ]iiany cases there is alsi.i a special ^■],■llld, known as the 

 " ink-ba;,' " (lig. 149, /;, for the secretion of an inky fluid, which the 

 animal disclmrges into tlie w;iter, so ,-is to enable it to escape wdien 

 menaced or ]inrsued. The duct of the inkdjag opens at the base of 

 the funnel near tlie .-111113 ; but the I'eaily X;iutihis and the allied 

 fossil forms are without this means of ilefeiice, which the presence of 

 an external shell renders unnecessary. 



The resjiir.-itory organs are in the form of plumedike gills, placed 

 on the sides of the body in a braiichi:d chainber, which ojieiis in 

 front oil the under surface of the body. In almost all the living 

 Cephahip,„l:i there are only two gills, one on e.'icli side, and hence 

 this section is known as th:it of the " I )ih/-:i ii::J,i,it,i." In the I'earh' 

 Nautilus alone there are biiir gills, two on each side, hence the name 

 of '■'■ Taruhriinrldatn'' .-ijiplieil to the order of which this is the only 

 living re]ireseiitative. In the Cuttle-fishes, at the base of each gill 

 is a .special contractile cavity, called a "branchial heart," bv wdiich 

 the venous blood, returned from the body, is dri\-en through the 

 gills. In iiddition to these branchial hearts there is a true arterial 

 heart, by which the aer:ited Ijlood recci\'ed from the gills is driven 



through the I ly. The admission of water to the branchia' is 



effected by the exjiansion of the mantle, which allows the entrance 

 of the outer water into the mnntle-cavity. The mantle then con- 

 tr.-icts, .-inil the Mater is forcibly expelled through tlie funnel, wdneh 

 is often furnished with a v.-dve, allowing the ]i;iss;ige of water out- 

 wards, but preventing its entrance iin\'ards. P.v a rejictition of this 

 ].rocess both respiration ■■iiid loeoniotion :ire siniultaneonsly effected, 

 for the jets of water exiiehed from the funnel by their reaction 

 drive the animal in the opposite direction, hi this case, therefore, 

 as in in;iiiy others, the more active the aiiimid is, the more perfectly 

 is the respiratory ]iro(,'ess c;irried on. 



The iicr\ous system is formeil upon essenti.'illy the .same ]ilan 

 as ill the other JA)///^^•.7r, but the great ner\e-eentres are col- 

 lected to form a, ring round the gullet, and are ]protected by a 

 cartitige, v.lrch is to be reg.-irdcd as w riulimentary .sl.cull. This 



