PHYSIOLOGY OF THE INVERTEHRATA. 



141 



haddock, aud 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 Cntstacca contains corpuscles which are 

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

 present a very distinct wall externally and nucleus within. 



The Mollusca. 



The blood of the lower MoUuscd (LamclHbranrhinfa 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 

 Anodonta and Mytiliis 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. Cuenott has recently shown that the blood from the heart 

 of Aplysia dcpilanH (one of the GasUropoda^ 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 Royal Society of Edinburgh 

 on June i, 1891 {P. 11. S. K., vol. 18, p. 288). 

 f Coiiqites Bendiis, vol. IIO, p. 724. 



