172 



Appendices to Fourth Annual Report 



readiness in the nephrops, is due to the oxygenation of a proteid body 

 which exists in solution in the blood plasma. The name hsemocyauin 

 was given to it by Fredericq. In the reduced state this body is colour- 

 less. The blue colour is often much obscured in the lobster and the 

 crayfish by a red pigment called tetronerythrin ; also iu solution in the 

 blood plasma. This pigment is also present in the blood of the nephrops, 

 but in such small quantities as not to obscure the blue colour due to oxy- 

 heemocyanin. 



Specific Gravity and Reaction. — The specific gravity of the blood varies 

 between 1025 and 1030. Its reaction is always faintly alkaline. 



Constituents. — The blood contains the following classes of bodies : — 

 (1.) Proteids or albuminous substances. 



(2.) Salts, which resemble those of the water in which the animal 

 lives, and are more abundant than in such an animal as the 

 common crayfish, which lives in fresh water. 

 (3.) Extractives. — Among these are a small amount of tetronerythrin, 

 a small amount of urea, and a varying quantity of certain fatty 

 bodies which I have not further examined. 

 The following table exhibits the average percentage proportions of these 

 constituents in the nephrops' blood, and in the blood of some other of the 

 commoner decapods, with which I have compared it : — 





Nephrops. 



Astacus. 



Lobster. 



Crab. 



Water 



89-06 



95-14 



93-49 



89-92 





10-94 



4-86 



6-51 



10-08 





4-60 



2-19 



3-02 



6.10 





3-57 



1-54 



•55 



1-28 



Salts 



2-77 



1-13 



2-94 



2-70 



Part II. — The Phenomena of Spontaneous Coagulation. 



Coagulation begins almost immediately the blood is shed, and the 

 coagulum that forms presents the appearance of a network of white fibres 

 throughout the liquid. This soon begins to contract, and squeezes out 

 drops of a perfectly clear liquid ; in a few minutes more this liquid, as 

 well as that between the fibres first formed, sets into a clear jelly. The 

 second process, or jellying, is in reality only a continuation of the first or 

 formation of the fibre-like clot. Both clots possess the same chemical 

 properties. The second or jelly-like clot finally contracts and squeezes 

 out serum. 



The substance of coagulation resembles very closely the fibrin of 

 vertebrate blood. Under the microscope it can be watched forming : at 

 first only the cells, which have the ordinary amoeboid characters described 

 in the blood of other Crustacea, are seen. Then they shoot out long pro- 

 cesses which interlace with one another. This was what Mr Geddes 

 {Proc. Roy. Soc, vol. 20, 1879-80) described as a Plasucodium. There 

 is, however, in addition, an intercellular substance of coagulation which is 

 distinctly fibrinous in appearance. The fibres which form have not such 

 a well-defined outline as the branches of the cells, and are therefore quite 

 easily distinguishable from them. The chemical properties of this 

 crustacean fibrin are also similar to those of vertebrate fibrin, with the 

 exception that it is not so readily soluble in weak solutions of neutral 

 salts, nor does it swell so markedly in weak hydrochloric acid. 



