BLOOD OF VARIOUS COLOURS. G7 



have blood of various colours, is probably news to you. 

 Swammerdamin* was the first who broke down the Aristo- 

 telian division, by showing that the blood of the earthworm 

 was red ; and Cuvier extended this observation to a whole 

 class of worms, to which he gave the name of Vers ct sang 

 rouge ; but this was vehemently criticised by De Blainville ; 

 and recent researches, especially those of Milne Edwards, 

 Quatrefages and Williams, have shown that a great diversity 

 in colour exists. Thus the Sea-Mouse (ApJirodita) has 

 colourless blood ; the Polynoe pale yellow ; the Sabella olive 

 green; and one sj)ecies of Sabella dark red. But this 

 difference of colour is trifling compared with the absence of 

 corpuscles from the blood of all Annelids. The corpuscles, 

 as you know, are the floating solids of the blood, and on 

 them devolve the most important physiological functions ; 

 but the blood of all Annelids is entirely destitute of them ; 

 and Milne Edwards, in noticing the fact, remarks that this 

 liquid resembles the imperfect blood of the vertebrate embryo 

 in the early periods of development.-|- 



There is one remark I wdsh to make in passing, respect- 

 ing the colourless blood of the majority of invertebrate 

 animals, and that is the proof it aflbrds of the error, not 

 uncommon, in attributing the colouring matter of animals 

 to the colouring matter of the blood. It is now known that 

 the colour of the muscles is due to a peculiar pigment, far 

 more than to the blood which is in them. It is quite clear 



* SWAMMERDAJIU : Biblia Naturce, i. 110. 



t Milne Edwakds : Lemons sur la Phys. el VAnut. Comparee, 1S57 ; vol. i. 

 p. 107. 



