CEPHALOPODA. 589 



branchia consists of a central stem supporting forty-eight vascular 

 plicated lamellae on each side : the smaller branchia has thirty-six 

 similar lamellae on each side. 



The four vessels (/,/} continued from the venous sinus have at- 

 tached to them, in their course to the gills, clusters of glandular 

 follicles {g, g) of a simple pyriform figure : each vessel has three 

 clusters of such glands contained in the membranous receptacles 

 above mentioned. The walls of these receptacles exhibit in some 

 parts a fibrous texture, apparently for the purpose of compressing 

 the follicles, and discharging the contents of the membranous recep- 

 tacles into the branchial cavity, by the apertures above mentioned at 

 the base of the gills. Doubtless, therefore, the glands are emunc- 

 tories, and eliminate from the venous blood an excretion, most pro- 

 bably urine. Their homologues exist in the higher Cephalopod, in 

 which they are considered to act as kidneys by Mayer ; and it is 

 more probable that the organs of so important an excretion should 

 be present in all the class, than that they should be represented by 

 the ink-gland and bag, which are peculiar to one order. 



The veins (f,f) extend beyond the follicles each to the root of its 

 respective gill, where it receives a small vein. At this part there is 

 a valve (A) which opposes the retrogression of the blood ; the vessel, 

 which may now be termed branchial artery, penetrates the root of 

 the gill (i), and dilates into a wider canal, which is continued through 

 the soft white substance forming the branchial stem. A double 

 series of branches are sent off from the lateral lamellaj^ which ramify 

 and subdivide to form the capillary plexus, from which the returning 

 vessels terminate in the branchial vein. These veins (/, I) quit the 

 roots of the gills, and return to terminate at the four corners of a 

 subquadrate transversely elongated ventricle (m). From this ven- 

 tricle two arteries arise, one superior and small (n), the other in- 

 ferior (r), and strengthened by a muscular bulb (q) to the extent of 

 nearly half an inch. An elongated pyriform sac (o) is attached by 

 a contracted origin near the root of the large aorta, and dilates to a 

 width of two lines ; then, again contracting, becomes connected by 

 its other extremity, to the venous sinus : it contained a firm coagu- 

 lated substance.* The anterior aorta supplies the nidamental 

 gland, and adjoining part of the mantle, and the rectum ; then bends 

 back to form the small artery (p), continued along the membranous 

 siphon (5). The large aorta supplies the gizzard and ovary, winds 

 round the bottom of the abdominal sac, sends off large branches to 

 the liver, and regains the dorsal aspect of the crop, along which it 



* CCCLXXXVII. p. 35. pi. 5. 18. 



