me 



OF CEPHALOPODA. 207 



Cephalopoda. As a representative of this order, I have 

 taken the common Squid, (figs. fol ^ f 



124, 125,) a species of Cuttle- 

 fish that abounds along our pv 

 sea-shores during the warmer P'j 

 months. It is represented here P v ' 



pa 



in a reversed position from that 



y 



in which it swims, in order to A 

 bring the organs into the same p 

 relation, in regard to up and 

 down, as those in the figures of 

 the Snail and the Oyster have. 

 It usually swims with its back downwards, as I have already 

 stated, (p. 121, note,) and most frequently backwards ; although it 

 moves with equal facility head foremost. In order to understand 

 its mode of swimming you have to learn that its body is en- 

 closed up to the neck in a loose muscular sac, (fig. 125, ma 1 ,) to 



the posterior aorta; a, a branch from ao l going to the mantle; hv, the posterior, 

 and hv 1 the anterior veins, which unite in a common reservoir at v, from whence 

 the blood enters the auricle (k) ; pa, the point of origin of the artery which 

 passes along the lower side of the gill (gl) ; pv, the branchial vein; pv 1 , point 

 of entrance of the blood from the gill, through pv, into the ventricle (/t 1 ) ; gl, 

 the left gill ; g^, the super-cesophageal nervous mass ; g l , the sub-ce soph age al ner- 

 vous mass, or lower half of the nervous collar ; op, the optic nerve, cut across ; 

 og, the superior, visceral nerve ; n, the mantle nerve ; e, the pupil of the eye ; 

 the outer, dotted circle indicates the outline of the eye ; ov, the reproductive 

 organ. Original. 



Fig. 125. The same as fig. 124, representing a diagramic view, from the pos- 

 terior end. ma 1 , the mantle; f, the funnel; ma, inferior edge of the membra- 

 nous, valvular prolongations (f l ) from the funnel ( /") ; me, cavity of the mantle; 

 sh, the shell; th, the throat; in, the mass which includes the posterior portion of 

 the intestine, the oviduct, and the ink-bag; Iv, lo l , the liver ; A 2 , A 3 , the right 

 auricle; h, the left auricle; A 1 , the ventricle; ao, the anterior aorta; pa, pa 1 , 

 the artery going to the gills (gF) ; pv, pv 1 , pv%, the branchial vein, emptying at 

 pv 1 into the ventricle (A 1 ) of the heart; gl, the gills, cut across; <7 2 , the super- 

 cesophageal, and g l , the sub-oesophageal, nervous mass; op, the optic nerve; e 1 , 

 the expansion of op at the back of the eye ; og, the superior, visceral nerve ; n, 

 the mantle nerves ; (og and n are dotted lines ;) ov, the reproductive organ. 

 Original. 



