Mr. Eobert Garner's Malacological Notes. 375 



of excretion. The lamellar mucous gland, seen in Buccinum 

 in the branchial chamber, is probably homologous with those 

 of the female Sepia ; there are also glandular parts for the 

 secretion of the purple or other colouring-matter, sometimes 

 simply a diffused gland in the mantle, whilst sometimes the 

 colouring liquid is received into a vesica as in Sepia^ Dorisj 

 or some Purpurce ; also renal organs, the latter opening, in the 

 branchiated Gastropods, at the far recess of the branchial 

 cavity, but by a long duct in the pulmonate animal. They 

 are near the mouth in Bullcea^ and open between the bran- 

 chial processes in Chiton^ near the double ovaries, but vari- 

 ously in bivalves * — sometimes in them into an aquiferous 

 chamber or double pleural sac, which also, according to Prof. 

 Rolleston, often communicates with the pericardium. These 

 renal organs commonly secrete little round concretions. The 

 organs themselves are less concentrated in Cephalopods ; but 

 the tufts on the veins and bile-ducts are, we think, their homo- 

 logues, excreting and not absorbing (at least entirely and 

 solely), the excretion being sometimes seen in the form of 

 yellowish glittering particles in the sac in which the tufts float, 

 and which sac communicates with the circumambient fluid by 

 two orifices, and also, in the opposite direction, with other mem- 

 branous cavities containing the viscera, or which are in appo- 

 sition to the spongy laminee of the shell in the Sepia. Water 

 no doubt has access to these cavities, and perhaps to others 

 situated about the head in Cephalopoda ( Tremoctopus or male 

 Argon aut)t, though the subocular pores in Sepia seem to be 

 excretory, and to lead down to glands situated beneath the 

 eye. Water has access likewise to the dorsal sinuses men- 

 tioned as existing in bivalves, and into their foot by means of 

 the median pedal pore in some species, or the lateral pseudo- 

 oviducts in others ; or into the laminae of the mantle, as seen 

 in opening a common Anodon. 



From the lowest mollusk to the highest there is the same 

 plan of nervous system, very different from that of the verte- 

 brate or articulate animal. The first nervous centre that 

 appears is the respiratory or branchial^, presiding over the 

 respiratory inlet and outlet in the Ascidia, and situated be- 

 tween the two orifices. Then the labial ganglia appear, in the 

 oyster for instance, and give off cords, which communicate 

 with the last, and, with their own uniting one, form a ring 

 round the mouth. In such bivalves as possess a foot another 

 ganglion or ganglionic pair supplies it, also communicating 

 with the labial ganglia, so that the ring becomes two-corded 



* Linn. Trans. 1836. 



t The species examined was perhaps Tremoctopus. 



\ A disputed point, however. 



26* 



