286 PHYSIOLOGY OF THE INVERTEBRATA. 



by the author.* Taking Se'pia officinalis as a type of the 

 Cephalopoda, it was proved that the nephridia of the animal 

 are true renal organs. The venous blood, as it passes from 

 the vena cava, is distributed by a number of afferent 

 branchial vessels which communicate with the sacculated 

 and glandular nephridia; it then passes into the branchias, 

 and hence it is sent back to the heart. 



The secretion of the nephridia contains uric acid and 

 calcium phosphate, but urea, guanin, calcium carbonate, and 

 magnesium carbonate are absent. 



Uric acid is also present in the blood of the vena cava 

 before it enters the nephridia, but the blood after passing 

 into the branchiae contains no uric acid. 



The nephridia of the Cephalopoda are true renal organs, 

 eliminating the nitrogenous waste matters in the form of 

 uric acid, contained in the impure blood as it is brought to 

 these organs by the vena cava. 



As already stated no urea could be detected in the nephridia 

 of Sepia, and the same remark applies to those of Octopus. 

 The muscular tissues of these animals do not yield urea ; but 

 it may be remarked that the muscular tissues of certain 

 Lamellibranchs do contain this base. For instance, loo 

 grammes each of the adductor muscles and foot of Mya 

 arenaria (large individuals) were chopped into small frag- 

 ments and were allowed to remain in contact with alcohol 

 for twelve hours. The alcohol was ,then squeezed out and 

 evaporated on a water-bath. The residue obtained was 

 dissolved in water, placed in the receiver of a mercury pump, 

 and treated with sodium hypobromite. By this method the 

 following results were obtained : — 



* Froc. Boy. Soc. Edin., vol. 14, p. 230. 



