70 SEA-SIDE STUDIES. 



secure them. And yet, apart from their beauty, the worms 

 deserve our study. Their structure is full of interest. 



Let us for a moment consider their blood. That some 



animals have red blood, and others blood not red (which 



made Aristotle say that some have blood and others 



none at all), you know perfectly well ; but that the 



worms have blood of various colours, is probably news 



to you. Swammerdamm '' was the first who broke 



down the Aristotelian 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 Vei^s a sang rouge ; but this was 



vehemently criticised by de Blainville ; and recent 



researches, especially those of Milne Edwards, Quatre- 



fages and Williams, have shown that a great diversity 



in colour exists. Thus the Sea-mouse (Aphrodita) has 



colourless blood ; the Polynoe pale yellow ; the Sahella 



olive green ; and one species of Sahella, dark red. But 



this diS'erence 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. •[* 



* Swammerdamm : BihliaNaturce, i. 119. 



t Milne Edwards : Lemons sur la Phys. et VAnat. Compar^e, 1857 ; 

 vol. i. p. 107. 



