1887 .] Dr A, B. Griffiths on Organs of the Invertebmta. 231 
small quantity of an aqueous solution of magnesium sulphate, with 
the production of a white precipitate of ammonio-magnesium 
phosphate. The presence of phosphoric acid in the earthy deposits 
was confirmed by using the ammonium molybdate and the uranium 
nitrate tests. Therefore, it must be concluded that these earthy 
deposits consist of calcium phosphate. No calcium carbonate, 
magnesium carbonate, nor any other compound was found in the 
deposit. 
Antr. vena 
cava. 
Nephridium 
(kidney). 
Ventricle. 
Vein. 
Capillaries. 
\ntr. aorta. 
* efferent bran- 
chial vessels. 
> Gill. 
> Afferent bran- 
chial vessels. 
Auricle. 
Post, vena cava. 
Post, aorta. 
Fig. 1. — Nephridium of Sepia officinalis. 
The liquid portion of the secretion of the nephridia was ex- 
amined by two separate methods : — 
(a) The clear liquid from the nephridia (after the separation of 
the calcium phosphate) was treated with a hot dilute solution of 
sodium hydrate, then on adding hydrochloric acid, a slight flaky 
precipitate is obtained ; and on examining these flakes under the 
microscope, they were seen to consist of small crystals in rhombic 
plates, prismatic needles, and stellar-shaped crystals. On treating 
the secretion with alcohol, the rhombic crystals are deposited ; 
these crystals are soluble in water. When these crystals are treated 
with nitric acid, and heated gently with ammonia, the reddish 
purple murexide [C s H 4 (NH 4 )N 6 O c ] is obtained, which was found 
crystallised in prisms. 
