PHYSIOLOGY OF THE INVERTEBRATA. 255 



To do this, the alcoholic solutioa was diluted with distilled 

 water, and boiled over a water-bath until all the alcohol had 

 vaporised. The warm aqueous solution (A) remaining was 

 now tested for urea in the following manner : — 



{(i) On the addition of mercuric nitrate to a portion of the 

 aboye solution, no white precipitate was obtained. 



(&) To another portion of the solution (A), a solution of 

 sodium hypochlorite was added. No bubbles of nitrogen 

 were disengaged. 



(c) No crystals of urea nitrate were formed in a small 

 quantity of the solution (A) [concentrated by evaporation] 

 after the addition of nitric acid. 



{d) The distillation of a small quantity of the solution (A) 

 with pure sodium carbonate in a chemically clean AVtirtz's 

 flask attached to a small Liebig's condenser, failed to produce 

 in the distillate any coloration with Nessler's reagent. 



The above tests clearly prove the entire absence of urea 

 in the excretion under examination. No guanin or calcium 

 phosphate could be detected in the excretion, although the 

 author has found the latter compound as an ingredient in 

 the renal excretions of the Crphalo})oda and the Lamclli- 

 hrancJiiata* 



From these investigations, the isolation of uric acid proves 

 the renal function of the five pouches or sacs of the stomach 

 of the Astcridca.'\ There is no doubt that the stomach of 

 starfishes performs a dual function : it is an excretory 

 organ as well as a digestive gland, and separates the nitro- 

 genous products of the waste of the tissues, &c., from the 

 blood or nutritive fluid in the form of uric acid, which is at 

 certain times to be found in the five pouches of that organ. 

 In the Invertcbrata there are numerous examples where an 

 organ performs a dual and even a triple function. 



* Proceed'uujs of Royal Society of Edinhuryh, vol. 14, p. 230. 

 •f See also Durham in Quart. Journ. Micros, h'clence, 1891. 



