1891-92.] Dr Griffiths on the Renal Organs of the Asteridea. 201 
this was not so, for urea is always absent in the true secretion of the 
cardiac sacs of the starfish’s stomach.* * * § 
Then again, the animals used in the investigation had been kept 
in a tank for very many days without food ; and to avoid any 
possible source of error, the alimentary canal had been previously 
washed out by injecting water through the oral aperture of each 
individual. This being done, each animal was then placed in a 
tank of water and kept as already stated for very many days before 
being used in the investigation. 
Further, it may be stated that the sacculated walls of the cardiac 
sacs of the stomach of Ur aster riibens take up indigo- carmine, and 
as A. Kowalewsky f has shown that this is characteristic of an 
excretory organ, we have additional evidence that these sacs in 
Ur aster perform the function of a renal organ. 
I am far from adversely criticising Mr Durham’s important work 
on the excretory nature of wandering cells in Echinoderms and 
other Invertebrates, but it should be distinctly understood that in 
Ur aster the cardiac sacs of the stomach form the chief apparatus by 
which uric acid is eliminated from the system. It is possible, nay 
probable, that wandering cells (carrying effete matter) may find 
their way to the cardiac sacs of the stomach of Uraster and other 
Asteridea. In fact, it may be stated that Shipley | considers that 
in the Hirudinea wandering cells may collect and carry effete 
products to the nephridial sacs, and after undergoing degeneration, 
these products are excreted through the nephridium or segmental 
organ. The secretion, or rather excretion, of the nephridia of 
Hirudo contains uric acid.§ 
Since my paper (loc. cit.) was published (in 1888), I have proved, 
by the same methods of investigation, that the stomach of Solaster 
and Astropecten also performs the function of a renal organ, for 
uric acid is readily extracted from the secretion of that organ. It 
* This statement may be readily confirmed when the proper tests are 
skilfully applied. I say “skilfully applied” because certain nitrogenous and 
other compounds have been said to he present in the secretion of the renal 
organs of many Invertebrates, which are not present at all. 
t Biologisches Centralhlatt, Bd. ix. (1889-90), pp. 33, 65, and 127. 
I Studies from Morphol. Labor., Cambridge, vol. 5 (1890). See also 
Vejdovsky’s System der Oligoeliceten, v., pp. Ill, 112, and 127. 
§ The author, in Proceedings of Royal Society of Edinburgh, vol. 14, p. 346. 
