FUNCTIONS OF BLOOD 111 



Thanks to the pronounced effect of C0 2 they utilize 80% or 

 more of the oxygen capacity, but the uptake of oxygen in the 

 gills will be seriously affected even by a few mm C0 2 pressure. 

 Octopus which often hides in narrow crevices in rocky shores 

 can stand fairly low oxygen tensions, and the same is the case 

 with Limulus and the gastropod Busycon. The inversion of the 

 CO2 effect in these latter forms is one of the obscure points. 

 The Crustacea examined were found to have identical dissocia- 

 tion curves. 



Chlorocruorins are found dissolved in the blood of serpulid 

 worms as a burgundy-red pigment of very nearly the same 

 colour in the oxidized and reduced state. They were studied 

 in several genera including Myxicoia, Spirographis and Sabella 

 by H. Munro Fox (1926, 1932). The pigments have very 

 large molecules, contain iron and are related to haemoglobins, 

 from which however they show very pronounced differences. 

 Fox found the oxygen affinity so low that the blood of Spiro- 

 graphis and some others could not even become fully saturated 

 in contact with atmospheric air. The oxygen capacity of 

 Spirographis blood was found to be 9.1 vols % in air and 10.2 in 

 oxygen. The dissociation curves are affected in the same 

 general way by temperature and COo as most haemoglobins, 

 and they combine with CO for which the affinity is higher 

 than for 2 . The chlorocruorins are efficient carriers of 

 oxygen at relatively high pressures (unloading tensions from 

 10 to 25 mm), but not adapted to the low tensions to which the 

 animals must be exposed when retiring into their tubes. 



Hcemerythrins are found only in corpuscles in the ccelomic 

 fluids of the class of sipunculoid worms, and appear to be 

 present in all the species belonging to this small group to the 

 exclusion of any other respiratory pigment. According to 

 Florkin (1933) they contain iron, but are not closely related 

 to the haemoglobins. They are stated to combine with oxygen 

 in the curious relation of 1 mole of 2 to 3 atoms of Fe and do 



