260 



Mr. J. L= Clarke on the Structure 



[Nov. 15, 



water, the solution on cooling depositing white silky needles of oxalurate 

 of silver. The lead compound produced by adding acetate of lead to the 

 watery solution, forms well-defined prismatic crystals. With chloride of 

 calcium the watery solution gives no precipitate, but on adding ammonia 

 and boiling, there is an abundant precipitation of oxalate of lime. By 

 treatment with strong acids the substance is decomposed, yielding oxalic 

 acid and urea. Its composition was found to correspond with the formula 

 Cg H7 Ng Og, which is that of oxalurate of ammonia. 



The author's experiments were not sufficiently numerous to decide the 

 question whether this salt is a normal constituent of human urine or not. 

 There is no doubt, however, that its presence, whether exceptional or not, 

 affords an easy and satisfactory explanation of a phenomenon which has 

 until now proved very puzzling, viz., the formation of oxalate of lime in 

 urine long after its emission. It is doubtless owing to the decomposition 

 of oxaluric acid, which takes up water and splits up into urea and oxalic 

 acid ; the latter then combines with lime, of which there is always a suffi- 

 cient quantity present to saturate the acid. ' There can be little doubt also 

 that oxaluric acid is derived in the animal frame, as in the laboratory, from 

 uric acid, the oxidation of which is its only known source. 



VI. " On the Structure of the Optic Lobes of the Cuttle-Fish.^' By 

 J. LocKHART Clarke, F.R.S. Eeceived September 26, 1866. 

 (Abstract.) 



The brain of the Cuttle-fish consists of several ganglia closely aggregated 

 around the upper part of the oesophagus. The foremost or pharyngeal 

 ganglion, which is much the smallest, is bilobed and somewhat quadran- 

 gular. The next is a large bilobed ganglion which forms the roof of the 

 canal for the oesophagus. Beneath the oesophagus is another large and 

 broad mass, which is connected on each side with the supra-cesophageal 

 masses by bands that complete the oesophageal ring. 



From each side of the cephalic masses springs a thick optic peduncle 

 which ends in the optic lobe. Each optic lobe is larger than all the other 

 cerebral masses taken together, and has a striking resemblance in shape to 

 the human kidney. It is completely enveloped in a thick layer of optic 

 nerves disposed in flattened bands which issue from all parts of its sub- 

 stance and proceed to the back of the eye in a fan-like expansion, the 

 upper and lower bands crossing each other in their course. The substance 

 of each lobe consists of two distinct portions, which differ from each other 

 entirely in appearance. The outer portion resembles a very thin rind or 

 shell, is extremely delicate, and very easily torn from the central substance 

 which it encloses. It consists of three concentric layers — an external 

 dark layer, an internal dark layer, and a middle pale and broader layer 

 containing thin and concentric bands of fibres. 



The first or outer layer consists of a multitude of nuclei and a few small 



