i66 PHYSIOLOGY OF THE INVERTEBRATA. 



tlieir food, because of the protective * colour which they 

 acquire from its presence in their blood and tissues. 



(4) The Arachnida. — Professor Eay Lankester f has shown 

 that the blood of Scorpio becomes blue . on exposure to air. 

 It contains h^mocyanin. The blood of Upeira, Tegenaria, 

 and Pholcus also contains hEemocyanin. 



(5) The Crustacea. — Concerning the blood of the Crustacea, 

 Genth in 1852 first observed the blue colour of the blood of 

 Limulus Cyclops; and in 1857, Professor Haeckel J observed 

 that the blue blood of Homarus became, after many hours' 

 exposure to the air, a violet colour. 



In 1873, Rabuteau and Papillon § experimented on the 

 blood of crabs, and found that it became blue in contact 

 with air, but lost this property when submitted to the action 

 of carbonic anhydride. It, however, recovered its blue colour 

 on shaking with air. " Jolyet and Regnard |1 showed in 1877 

 that on shaking crabs' blood with air it showed a beautiful 

 blue or brownish colour, according to the manner in which it 

 was examined; it gradually loses this colour, becoming reddish 

 and then feebly yellow ; but on treatment with pure oxygen 

 its original colour is restored. They found two colouring 

 matters in crabs' blood : one is blue, and is precipitated by 

 alcohol with the albumin of the blood ; the other is reddish, 

 and remains in the alcoholic filtrate." 



In 1879, Dr. L^on Predericq % proved that the blue blood of 

 Homarus contained hsemocyanin, and that it was blue with 

 reflected and brown with transmitted light. The blue pigment 

 — h^mocyanin — is aproteid containing copper. The red pig- 

 ment in crabs' blood is also present in the blood of SomarvA 

 But this pigment does not belong to the proteid constituents 

 of the blood ; it does not contain copper, iron, or manganese, 



* From enemies. 



t Quarterly Jourtml of Microscopical Science, 1878, p. 453. 



J Midler's Archiv, 1857, p. 511, Anm, i. 



§ Comptes-Bendus, t. 77, p. 137. 



II Archives lie Physiologic, 2 s^rie, t. 47. 



^ Bulletins de I' Academic Boyale de Belgique, 2 serie, t. 47. 



