CEPHALOPODA. 455 



urinary secretion ; so that, according to this view, the anatomist 

 referred to does not scruple to designate the chamber called by 

 Professor Owen " the pericardium " as a urinary bladder, and to 

 the two orifices leading from thence to the cavity in which the 

 branchiae are lodged he would assign the name of urethra. Pro- 

 fessor Owen has suggested that, in addition to their subserviency 

 to secretion, these appendages to the veins of Cephalopods may 

 be provisions for enabling their sanguiferous system to accommo- 

 date itself to those vicissitudes of pressure to which it must be 

 constantly subjected, and that they bear a relation to the power 

 possessed by these animals of descending to great depths in the 

 ocean, thus answering the same purpose as the capacious auricle, 

 and the large venous sinuses that terminate in the heart of 

 fishes. According to this view, these follicles relieve the vascular 

 system, by affording a temporary receptacle for the blood when- 

 ever it accumulates in the vessels, owing to a partial impediment 

 to its course through the respiratory organs, serving in this man- 

 ner to regulate the quantity of blood sent to the branchiae.* 



(497.) In Nautilus Professor Owen found, in addition to the 

 spungoid appendages connected with the veins, lodged in what he 

 denominates the " pericardium" that the great trunk of the vena 

 cava itself presents a structure precisely analogous to what has been 

 already described when speaking of the venous system of Aptysia 

 among the GASTEROPODA (^ 443), namely, a free communication 

 between the interior of the vein and the cavity of the peritoneum. ~f* 

 The vein is of a flattened form, being included between a strong 

 membrane on the lower or ventral aspect, and a layer of transverse 

 muscular fibres which decussate each other on the upper or dorsal 

 aspect. The adhesion of the coats of the vein to the muscular 

 fibres is very strong, and these fibres form in consequence part of 

 the parietes of the vein itself throughout its whole course. But 

 there are several small intervals left between the muscular fasciculi 

 and corresponding round apertures both in the vein and in the 

 peritoneum, so that the latter membrane at these points seems to 

 be continuous with the lining membrane of the vena cava. The 

 distinguished anatomist referred to counted as many as fifteen of 

 these openings, and most of them were sufficiently large to admit 

 the head of an eye-probe. Here, therefore, as in Aplysia, there 

 are direct communications between the interior of the vena cava and 

 the great serous cavity of the abdomen ; and, moreover, in both in- 



* Mem. on Nautilus Pomp. p. 34. f Mem. on the Pearly Nautilus, p. 72. 



