PHYSIOLOGY OF THE INVERTEBRATA. 



141 



haddock, and a weever does not contain more soluble salts 

 than the blood of fresh water fishes. 



Among fishes the interior fluid constituting the blood is 

 isolated more or less from the external medium in which the 

 animal lives. In regard to this there is an advance on that 

 which occurs among Invertebrates. 



The blood of the Crustacea contains corpuscles which are 

 very well defined. They are oval in shape, granular, and 

 present a very distinct wall externally and nucleus within. 



The Mollusca. 



The blood of the lower Mollusca (Zamellibranchiata and 

 Gasteropoda) is corpusculated, but the nuclei (which are 

 generally present) are sometimes very indistinct. 



The percentages of saline matter contained in the blood of 

 A'rwdonta and Mytilus were found to be the following* : — 



It will be observed that the blood of the fresh water 

 mussel contains a smaller amount of saline matter than that 

 of the marine form. 



The blood of the Mollusca is principally colourless, but Dr. 

 L. Ougnotf has recently shown that the blood from the heart 

 of Aplysia depilans (one of the Gasteropoda) has a distinct 

 rose colour, due to the presence of 0.636 per cent, of an 

 albuminoid which is precipitated by alcohol, acids, mercuric 

 chloride, and the usual reagents. Its colour has no relation 

 to the presence of oxygen, and it seems improbable that it 

 plays any part in respiration. When the blood is dialyzed, 



* See Dr. Griffiths' paper read before the Koyal Society of Edinburgh 

 on June i, 1891 (P. B. K E., vol. 18, p. 288). 

 t Comptes Rendus, vol. no, p. 724. 



