THE CEPHALOPODA 309 



thence into the respiratory vessels of the branchia for oxygenation 

 before it is finally carried to the heart. 



3. Excretory Apparatus. The coelom of the Cephalopoda is very 

 extensive. It comprises the gonocoele and the pericardial coelom ; 

 these cavities communicate freely with one another (Fig. 252, coe) 

 and are only separated by an incomplete septum, which is atrophied 

 in Sepia. In Nautilus this coelom extends into the aboral region of 

 the body and its genital division which communicates with the 

 pericardial division by three orifices in the septum passes into the 

 dorsal region and extends nearly as far forward as the middle of the 



Fio. 275. 



View of the ventral surface of a male Nautilus, the mantle-skirt being completely reflected 

 so as to show the inner wall of the sub-pallial Chamber and the four ctenidia and the foot cut 

 short, a, muscular band, passing from the funnel to the integument ; an, anus ; c, mantle- 

 skirt ; l.sp, aperture of the rudimentary left spermiduct ; neph.a, aperture of the left anterior 

 kidney ; neph.p, aperture of the right posterior kidney ; olf, protective papilla of the osphra- 

 dinm ; pe, penis ; visc.per, left aperture of the viscero-pericardial sac ; x, post-anal papilla. 

 (After Lankester.) 



oesophagus (Fig. 270, x). But the pericardial coelom is a flattened 

 ventral cavity situated immediately beneath the body- wall : it contains 

 the heart with its four auricles (Fig. 274) and the pericardial glands 

 or portions of the follicular glandular appendages of the branchial 

 vessels. In the Dibranchia, the coelom of the Decapoda contains 

 the heart, the gonad, and the branchial hearts with their glandular 

 appendages (pericardial glands, Fig. 273, c.b, x), but it is so much 

 reduced in the Octopoda that it contains only the gonads and the 

 appendages of the branchial hearts, its anterior part having dis- 

 appeared (Fig. 278). 



In the Decapoda the coelorn forms a vast pouch, with a 

 constriction between the posterior or genital division and the 

 anterior pericardial division, and it is produced into lateral annexes 



