348 Proceedings of Royal Society of Edinburgh. [july 4, 
crystals. According to tlie test of Dr Schiff {Ann. Chem. Pliarm ., 
vol. cix. p. G7) for uric acid, these crystals were dissolved in a drop 
or two of sodium carbonate solution, and then poured upon a piece 
of filter-paper moistened with a solution of silver nitrate : a dark 
brown stain of metallic silver was obtained. 
(b) Another process was used as follows : — To the liquid secreted 
by the nephridia of Hirudo boiling water (distilled) was added, and 
then evaporated carefully to dryness. The residue so obtained was 
treated with absolute alcohol, and filtered. Boiling water was 
poured upon the residue, and an excess of acetic acid added to the 
filtrate (aqueous). After standing several hours, crystals of uric 
acid made their appearance, and were easily recognised by the 
chemical and microscopical tests mentioned above. 
Further than this, the presence of sodium was found in the secre- 
tions of the nephridia of Hirudo. It may be that the uric acid is 
in combination with sodium as a sodium urate. 
From this investigation the nephridium of the Hirudinea func- 
tions as a true kidney. 
Renal Organs of the Hirudinea aud Oligochceta and their 
Constituents. 
Hirudinea. 
Oligocliafia. 
Uric acid, ..... 
Sodium, .... . . 
Urea, ...... 
Guanin, ...... 
Calcium phosphate, 
present. 
99 
absent. 
99 
9 9 
present. 
absent. 
9 9 
9 y 
99 
The minute structure of the excretory organs in general of the 
Oligochseta, especially those of Lumbricus terrestris, have been 
worked out by Dr E. Claparede, and detailed in his “ Histologische 
Untersuchungen fiber den Regenwurm ” {Zeitsclirift fur Wissen- 
schaftliche Zoologie , vol. xix.), and also by Professor Gegenbaur, 
“ Ueber die sogenannten ftespirationsorgane des Regen wurms ” 
{Zeitsch. W. Zool ., vol. iv.). 
