220 PHYSIOLOGY OF THE INVERTEBRATA. 



MacMunn* lias discovered various pigments in the tissues 

 and organs of the Echinoderms ; and in most of them the 

 appearances differ in no respect from those seen in Uraster 

 ruhens. 



A portion of the tissue or organ is examined in a compres- 

 sorium, by means of which any required thickness can be 

 examined : it is illuminated by a strong light condensed upon 

 it by means of a substage achromatic condenser, and is 

 examined by a microspectroscope (see Fig, 32), or by means 

 of a chemical spectroscope. 



The generative organs ( $ and 2 ) and ova of Uraster 

 contain a typical histoheematin. The spectrum of this pig- 

 ment gave the following readings : — 



ist band .... X 613 to X 591, or 593. 



2nd ,, .... X 569 „ X 560. 



3rd „ . . . . X 556 „ X 548-5. 



4th , X 537 „ X 516 (about). 



A spectroscopic examination of the stomach-wall and the 

 ampullae of Uraster showed the presence of hasmochromogen. 



"In the integument of Uraster ruhens, when it has a 

 brownish tint, the presence of hsematoporphyrin j can be 

 easily proved, and as the only pigments present in the animal 

 are enterochlorophyll in the radial cfeca, liistohfematins in the 

 tissues, and a lipochrome here and there, and as haamato- 

 porphyrin cannot be obtained from enterochlorophyll or from 

 the lipochromes, it is highly probable it is a metabolite of the 

 histohaamatins, or, what is less likely, that these pigments niay 

 be derived from the same radicle." 



M. Fcettinger states that he found haemoglobin in Opliiaetis 

 virens and MacMunn's researches tend to support Foettinger's 

 idea of the passage from a histohaematin to a hasmoglobin. 



* I'hilosoph. Trans., 1886, pt. i. p. 269 ; Quarterly Juurn. Jlicros. iSiience, 

 vol. 30, p. 51 ; Journal of Thy biology, vol. 7, p. 242. 



t This pigment can be isolated by digesting the integument in alcohol 

 and sulphuric acid. 



