238 PHYSIOLOGY OF THE INVERTEBRATA. 



lijematins have been discovered in various parts of the body ; 

 and haemoglobin occurs in the pharyngeal muscles of the 

 foUowino- Molluscs: Purpura Icqnllus, Littoriim littorea, 

 Trochus cinerarius, Patella vulgata, LimnceiLS stagnalis, and 

 Paludina vivipara. 



Myohasmatin is the histohfematin characteristic of In- 

 vertebrate muscle, but in the above-mentioned species this 

 pigment is replaced by hiL-moglobin.* This proves that 

 the histohffimatins are connected with heeraoglobin and its 

 derivatives. 



j\[yohtematin occurs in all the Pulmnfjastcropoda examined 

 by MacMunn. " Myohasmatin is the true intrinsic colouring 

 matter of muscle, and the histohasmatins the intrinsic colour- 

 ing matters of the tissues and organs ; both may be reinforced 

 or replaced at times by hasmoglobin when extra activity of 

 internal respiration is required; probably the same radicle 

 may be made use of for building up all these pigments, for 

 they seem to be related, since the same decomposition product 

 — hfematoporphyrin — is probably yielded by all of them. 

 The fact that in the lower animals pigments of less complex 

 molecular structure than hasmoglobin and identical with its 

 decomposition products can function like it, forces itself 

 on anyone's attention who studies the pigments of the 

 Piiocrtcbrata.^^ 



MacMunn has extracted hasmatoporphyrin from the in- 

 tegument of Limax fiavus, Limaic varic;/atics, Arioii atcr, and 

 Solccwrtus strigillatus. With the exception of Solecurtus, in 

 all these Molluscs enterohae matin is found in the so-called 

 liver (pancreas), and histohtematins in various tissues and 

 organs, and there can be no doubt, as MacMunn states, that 

 here also the heematoporphyrin is a metabolite of these 

 pigments. 



, The so-called livers of the ■ following Molluscs contain 

 enterochlorophylls which are identical with Krukenberg's 

 hepatochromates : Ostrcca, Pitccinuni, Fusus, Mytilus, Cardium, 



* The blood of Solen leyumen contains hjemoglobin (Lankester). 



