CEPHALOPODA. 



435 



region of the mantle-cavity (Fig. 348, It). In Dibranchs (Fig. 349) 



the perivisceral part of the coelom is also in two communicating 



parts: (1) the genital division, which opens to the exterior by the 



genital duct, and is related only to the gonad ; and (2) the viscero- 



pericardial which has relations to the heart, stomach, intestine, 



branchial hearts, and pericardia! glands (Decapoda), and does not 



open to the exterior. In Odopoda (Fig. 350) the viscero-pericardial 



coelom is prac- 



tically absent, 



being reduced to 



a small space 



(VI) on each 



side round the 



glandular appen- 



dages of the 



branchial heart 



(pericardial 



glands), which 



opens ( VII) into 



the nephridilini 

 and COm muni- 



Gates bv a narrow 

 *> ' 



Canal (//) with 



the apically- 



placed genital division of the coelom. In Dibranchs the perivisceral 

 (viscero-pericardial) part of the coelom also communicates with the 

 kidneys, and not directly with the exterior (Fig. 349, XVI I\ whereas 

 in Nautilus it has no opening into the kidney. 



The branchiae have the form of two (Dibranchiata) or four 

 (Tetrdbrancliiata) bilamellate ctenidia, which are placed on the 

 visceral sac in the mantle-cavity, and are not ciliated. In Nautilus 

 they project freely and the posterior are a little larger than the 

 anterior; in Dibranchs they are attached to the body along one 

 side of the axis. 



Osphradia are absent in Dibranchs, but in Nautilus there are two 

 pairs of papillae in the mantle-cavity, which are supposed to repre- 

 sent them. The anterior pair is between the two pairs of gills 

 (Fig. 348, (7), while the posterior osphradia* are the so-called post- 

 anal papillae placed near together on the mantle between the renal 

 sacs and the nidamental glands in the female, and in the same 



IV 



IG - 350. Diagram of the coelom of a female Octopus, ventral 

 (posterior) view (from Pelseneer, after Brock). / branchial heart ; 

 //canal connecting the genital and visceral parts of the coelom; 

 Ul oviducts ; ir oviducal gland ; V appendage of branchial heart ; 

 VI perivisceral (pericardial) coelom ; VII reno-pericardial opening ; 

 VIII ovary ; IX genital coelom. 



Fide A. Willey, Q. J. M. S., 40, 1897. 



