238 PHYSIOLOGY OF THE INVERTEBRATA. 



hEematins have been discovered in various parts of the body; 

 and hEsmoglobin occurs in the pharyngeal muscles of the 

 following Molluscs: Puiyura lapillus, lAttorina littwea, 

 Trochus cinerarius, Patella milgata, Limnceus stagnalis, and 

 Paludina vivipara. 



Myohaematin is the histohsematin characteristic of In- 

 vertebrate muscle, but in the above-mentioned species this 

 pigment is replaced by haemoglobin.* This proves that 

 the histohsematins are connected with hEemoglobin and its 

 derivatives. 



Myohaematin occurs in all the Pulmog aster opoda examined 

 by MacMunn. " Myohaematin is the true intrinsic colouring 

 matter of muscle, and the histohsematins the intrinsic colour- 

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

 or replaced at times by hemoglobin 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 

 — hsematoporphyrin — is probably yielded by all of them. 

 The fact that in the lower animals .pigments of less complex 

 molecular structure than haemoglobin and identical with its 

 decomposition products can function like it, forces itself 

 on anyone's attention who studies the pigments of the 

 InvertArata." 



MacMunn has extracted haematoporphyrin from the in- 

 tegument of Limax flavus, Umax variegatus, Arion ater, and 

 Solecurtus strigillatus. With the exception of Solecurtus, in 

 all these Molluscs enterohaematin is found in the so-called 

 liver (pancreas), and histohsematins in various tissues and 

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

 here also the haematoporphyrin is a metabolite of these 

 pigments. 



The so-called livers of the j folio wing Molluscs contain 

 enterochlorophylls which are identical with Krukenberg's 

 hepatochromates: Ostrcea, Piiccinum, Fusus, Mytilm, Cardium, 

 * The blood of Solen legumen contains hemoglobin (Lankester). 



