PHYSIOLOGY OF THL INVERTEBRATA. 149 



lipochromes included under the name tetronerythrin by 

 Merejkowsky " fail to respond to the test used in determining 

 whether any pigment is respiratory or not, namely, change 

 of colour and spectrum under the influence of reducing 

 agents." 



Dr. Mac]\Iunn* has also investigated the brown colouring 

 matter of the perivisceral fluid of Echinus (esadentus /) and 

 sp/ucm. This colouring matter gave two bands, one between 

 D and E covering E, and the other between b and F, the first of 

 which became decidedly darker after the addition of ammo- 

 nium sulphide. MacMunn named this pigment echinochrome, 

 and it has a respiratory function. 



Since his discoverv of echinochrome, MacMunn has made 

 some valuable observations on the perivisceral fluid of 

 Strongyloccntrotus lividus. On opening a specimen a pale red 

 fluid exudes from the perivisceral cavity. " In a short time 

 a clot forms ; this becomes gradually darker in colour and it 

 contracts more and more, until all its connections with the 

 side of the containing vessel are broken, and it finally 

 shrinks into a small brown-red mass. The corpuscles are 

 carried down by this clot, and it is to them, not to the 

 plasma, that the colouring matter belongs," Prof. P. Geddes f 

 (who has worked out the morphology of the corpuscles of the 

 perivisceral fluid of various Echinoderms) has shown that the 

 finely granular, pale corpuscles run together to form plas- 

 modia, and that it is to their fusion that the clotting is due. 



" The corpuscles present all degrees of coloration, from a 

 brilliant red, through a pale orange, to colourless. The red 

 ones are nucleated and of irregular shape, and rapidly throw 

 out amfjcboid processes, so also do the others. The nucleus is 

 strongly refracting and gives the corpuscles the appearance of 

 a round hole having been punched in it. The red corpuscles 

 measure from t^Vo inch in long diameter x j^^^^ inch in 

 short, down to ^joVo i" long x ^jj„^ in short, while several 



* Prere.edi iifjs of BirmiiKjham Philosophical Society, vol. 3, p. 380. 

 t Proc. Hoy. Soc., 1880. 



